Reduced levels of active GLP-1 in patients with cystic fibrosis with and without diabetes mellitus

The Changing Landscape of Treatment for Cystic Fibrosis Related Diabetes

Objective

Patients with Cystic Fibrosis related diabetes [CFRD] are treated with insulin and high calorie diets to maintain body mass. The combined CFTR modulator elexacaftor/tezacaftor/ivacaftor [ETI] decreases pulmonary exacerbations and improves nutritional status. We reviewed the effects of ETI on BMI, HbA1c and diabetes regimen in patients with CFRD over a period of three years.

Methods

Data of previously CFTR-modulator-naïve patients with CFRD and pancreatic insufficiency on ETI therapy were retrieved from an electronic health record database. Patients were followed for a mean duration of 2.7 ± 0.8 years after ETI initiation. Data pertaining to weight, BMI, HbA1c and diabetes regimen were collected at 6 months, 12 months, 2 years and at 3 years post-ETI initiation. Patients were then dichotomized based on their baseline BMI into a low BMI group and an "at target" BMI group. The effects of ETI on changes in weight, BMI, A1c and diabetes regimen were compared in both groups over a period of three years.

Results

Twenty-seven patients with CFRD (15 men/12 women), age 30.6 ± 11.5 (SD) years, BMI 22.4 ± 4.0 kg/m2, were included. Fifteen patients had low BMI (<22 kg/m2 for women, <23 kg/m2 for men) and 12 patients had at target BMI (≥22 kg/m2for women, ≥BMI 23 kg/m2 for men). Patients with low BMI had an increase in their BMI from 19.5 ± 1.7 to 21.4 ± 2.2 kg/m2 at one year (p = 0.002), and 21.8 ± 1.8 kg/m2 at three years (p = 0.004) after ETI initiation. Four patients (out of 15) in the low BMI group had achieved normal BMI by the end of study follow up. There was no change in weight in the at target BMI group. HbA1c and basal insulin requirements did not change in either group. Five patients started non-insulin therapies.

Conclusion

BMI increased after ETI therapy in CFRD patients with low BMI, but not in those with at target BMI. The use of non-insulin therapies is increasing in CFRD and should be evaluated in future studies.

Early-phase insulin secretion during mixed-meal tolerance testing predicts β-cell function and secretory capacity in cystic fibrosis

Insulin secretion within 30 minutes of nutrient ingestion is reduced in people with cystic fibrosis (PwCF) and pancreatic insufficiency and declines with worsening glucose tolerance. The glucose potentiated arginine (GPA) test is validated for quantifying β-cell secretory capacity as an estimate of functional β-cell mass but requires technical expertise and is burdensome. This study sought to compare insulin secretion during mixed-meal tolerance testing (MMTT) to GPA-derived parameters in PwCF.

Methods

Secondary data analysis of CF-focused prospective studies was performed in PwCF categorized as 1) pancreatic insufficient [PI-CF] or 2) pancreatic sufficient [PS-CF] and in 3) non-CF controls. MMTT: insulin secretory rates (ISR) were derived by parametric deconvolution using 2-compartment model of C-peptide kinetics, and incremental area under the curve (AUC) was calculated for 30, 60 and 180-minutes. GPA: acute insulin (AIR) and C-peptide responses (ACR) were calculated as average post-arginine insulin or C-peptide response minus pre-arginine insulin or C-peptide under fasting (AIRarg and ACRarg), ~230 mg/dL (AIRpot and ACRpot), and ~340 mg/dL (AIRmax and ACRmax) hyperglycemic clamp conditions. Relationships of MMTT to GPA parameters were derived using Pearson's correlation coefficient. Predicted values were generated for MMTT ISR and compared to GPA parameters using Bland Altman analysis to assess degree of concordance.

Results

85 PwCF (45 female; 75 PI-CF and 10 PS-CF) median (range) age 23 (6-56) years with BMI 23 (13-34) kg/m2, HbA1c 5.5 (3.8-10.2)%, and FEV1%-predicted 88 (26-125) and 4 non-CF controls of similar age and BMI were included. ISR AUC30min positively correlated with AIRarg (r=0.55), AIRpot (r=0.62), and AIRmax (r=0.46) and with ACRarg (r=0.59), ACRpot (r=0.60), and ACRmax (r=0.51) (all P<0.001). ISR AUC30min strongly predicted AIRarg (concordance=0.86), AIRpot (concordance=0.89), and AIRmax (concordance=0.76) at lower mean GPA values, but underestimated AIRarg, AIRpot, and AIRmax at higher GPA-defined β-cell secretory capacity. Between test agreement was unaltered by adjustment for study group, OGTT glucose category, and BMI.

Conclusion

Early-phase insulin secretion during MMTT can accurately predict GPA-derived measures of β-cell function and secretory capacity when functional β-cell mass is reduced. These data can inform future multicenter studies requiring reliable, standardized, and technically feasible testing mechanisms to quantify β-cell function and secretory capacity.

Bariatric surgery in a patient with cystic fibrosis and diabetes: A case report

Cystic fibrosis (CF) is incurable and chronic, causing severe multisystemic damage and long-term complications. The most prominent extrapulmonary long-term complication is CF-related diabetes, which is the most reported form of diabetes in individuals with cystic fibrosis. Here we present the first case of an individual with cystic fibrosis who developed type 2 diabetes due to obesity rather than CF-related diabetes. The type 2 diabetes went into remission due to extreme weight loss after gastric bypass surgery. To our knowledge, this case is also the first report describing the effect of bariatric surgery in a patient with CF. This case demonstrates that patients with CF may present with type 2 diabetes instead of CF-related diabetes. Differential diagnosis of these two types of diabetes is essential for optimal treatment and quality of life.

Bone metabolism and incretin hormones following glucose ingestion in young adults with pancreatic insufficient cystic fibrosis

Background

Gut-derived incretin hormones, including glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 (GLP-1), regulate post-prandial glucose metabolism by promoting insulin production. GIP, GLP-1, and insulin contribute to the acute bone anti-resorptive effect of macronutrient ingestion by modifying bone turnover. Cystic fibrosis (CF) is associated with exocrine pancreatic insufficiency (PI), which perturbs the incretin response. Cross-talk between the gut and bone ("gut-bone axis") has not yet been studied in PI-CF. The objectives of this study were to assess changes in biomarkers of bone metabolism during oral glucose tolerance testing (OGTT) and to test associations between incretins and biomarkers of bone metabolism in individuals with PI-CF.

Methods

We performed a secondary analysis of previously acquired blood specimens from multi-sample OGTT from individuals with PI-CF ages 14-30 years (n = 23). Changes in insulin, incretins, and biomarkers of bone resorption (C-terminal telopeptide of type 1 collagen [CTX]) and formation (procollagen type I N-terminal propeptide [P1NP]) during OGTT were computed.

Results

CTX decreased by 32% by min 120 of OGTT (P < 0.001), but P1NP was unchanged. Increases in GIP from 0 to 30 mins (rho = -0.48, P = 0.03) and decreases in GIP from 30 to 120 mins (rho = 0.62, P = 0.002) correlated with decreases in CTX from mins 0-120. Changes in GLP-1 and insulin were not correlated with changes in CTX, and changes in incretins and insulin were not correlated with changes in P1NP.

Conclusions

Intact GIP response was correlated with the bone anti-resorptive effect of glucose ingestion, represented by a decrease in CTX. Since incretin hormones might contribute to development of diabetes and bone disease in CF, the "gut-bone axis" warrants further attention in CF during the years surrounding peak bone mass attainment.

Association of Islet Amyloid Polypeptide to C-Peptide Ratio With Cystic Fibrosis-Related Diabetes: A Prospective Cross-sectional Study

OBJECTIVES

Early detection of cystic fibrosis (CF) related diabetes (CFRD) improves health outcomes and reduces CF-related mortality. The study aims to evaluate the ratio of islet amyloid polypeptide (IAPP) to C-peptide in CF patients with diabetes and without diabetes.

METHODS

Cross-sectional analysis was carried out in a prospective cohort of 33 participants (CF [n = 16] and CFRD [n = 18]). We examined the association of plasma IAPP:C-peptide ratio with clinical information, including glycated hemoglobin, and lung function markers.

RESULTS

The median (interquartile range) IAPP:C-peptide ratio was significantly (P = 0.004) higher in people with CFRD (4.8 [4.5]) compared with participants without CFRD (12.1 [19.7]). The ratio of IAPP to C-peptide significantly accounted for a 38% variation in the diabetes status in patients with CF (r2 = 0.399, P < 0.001). Islet amyloid polypeptide is strongly correlated with serum ferritin levels (r = 0.683, P = 0.005) and forced expiratory volume in CFRD, but not in nondiabetic participants with CF.

CONCLUSIONS

Islet amyloid polypeptide:C-peptide ratio could be a potential marker of CFRD in adults with CF. Further research requires validation of this marker in longitudinal cohort studies to confirm the capability of IAPP:C-peptide to predict CFRD.

New Concepts in the Pathogenesis of Cystic Fibrosis-Related Diabetes

CONTEXT

Cystic fibrosis-related diabetes (CFRD) is the most common extrapulmonary complication of cystic fibrosis (CF). Approximately 40% of people with CF who are older than 20 years have CFRD. Presence of CFRD is associated with poor health outcomes in people with CF.

OBJECTIVE

This review summarizes current knowledge on pathophysiology of CFRD.

METHODS

A PubMed review of the literature was conducted, with search terms that included CFRD, cystic fibrosis, cystic fibrosis related diabetes, and cystic fibrosis transmembrane conductance regulator (CFTR). Additional sources were identified through manual searches of reference lists. Pathophysiology of CFRD: The pathophysiology underlying development of glucose tolerance abnormalities in CF is complex and not fully understood. β-cell loss and functional impairment of the remaining β-cell function results in progressive insulin insufficiency. Factors that may contribute to development of CFRD include local islet and systemic inflammation, alterations in the incretion hormone axis, varying degrees of insulin resistance and genetic factors related to type 2 diabetes.

CONCLUSION

The prevalence of CFRD is expected to further increase with improving life expectancy of people with CF. Further research is needed to better understand the mechanisms underlying the development of CFRD and the impact of diabetes on clinical outcomes in CF.

Alterations of mucosa-attached microbiome and epithelial cell numbers in the cystic fibrosis small intestine with implications for intestinal disease

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Defective CFTR leads to accumulation of dehydrated viscous mucus within the small intestine, luminal acidification and altered intestinal motility, resulting in blockage. These changes promote gut microbial dysbiosis, adversely influencing the normal proliferation and differentiation of intestinal epithelial cells. Using Illumina 16S rRNA gene sequencing and immunohistochemistry, we assessed changes in mucosa-attached microbiome and epithelial cell profile in the small intestine of CF mice and a CF patient compared to wild-type mice and non-CF humans. We found increased abundance of pro-inflammatory Escherichia and depletion of beneficial secondary bile-acid producing bacteria in the ileal mucosa-attached microbiome of CFTR-null mice. The ileal mucosa in a CF patient was dominated by a non-aeruginosa Pseudomonas species and lacked numerous beneficial anti-inflammatory and short-chain fatty acid-producing bacteria. In the ileum of both CF mice and a CF patient, the number of absorptive enterocytes, Paneth and glucagon-like peptide 1 and 2 secreting L-type enteroendocrine cells were decreased, whereas stem and goblet cell numbers were increased. These changes in mucosa-attached microbiome and epithelial cell profile suggest that microbiota-host interactions may contribute to intestinal CF disease development with implications for therapy.

Islet Function in the Pathogenesis of Cystic Fibrosis-Related Diabetes Mellitus

Cystic fibrosis-related diabetes mellitus (CFRD) is the most common non-pulmonary co-morbidity in cystic fibrosis (CF). CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR), which leads to aberrant luminal fluid secretions in organs such as the lungs and pancreas. How dysfunctional CFTR leads to CFRD is still under debate. Both intrinsic effects of dysfunctional CFTR in hormone secreting cells of the islets and effects of exocrine damage have been proposed. In the current review, we discuss these non-mutually exclusive hypotheses with a special focus on how dysfunctional CFTR in endocrine cells may contribute to an altered glucose homeostasis. We outline the proposed role of CFTR in the molecular pathways of β-cell insulin secretion and α-cell glucagon secretion, and touch upon the importance of the exocrine pancreas and intra-pancreatic crosstalk for proper islet function.

Chronic incretin-based therapy in cystic fibrosis-related diabetes: A tale of 3 patients treated with sitagliptin for over 5 years

Cystic fibrosis-related diabetes (CFRD) affects 40-50% of adult patients with cystic fibrosis. Insulin therapy is recommended but there are therapeutic challenges, particularly risk of hypoglycemia and aversion of some patients to injectables. An oral incretin-based therapy using a DPP-4i (dipeptidyl peptidase-4 inhibitor), may be a reasonable option, especially in the early stage of the disease. The effect of chronic incretin-based therapy on CFRD is unknown. Here is a report of 3 cases of CFRD patients treated with sitagliptin and the response to therapy over a period of 5-10 years. An effective glycemic control was demonstrated in all the patients, at least during the first 5 years of sitagliptin treatment, and the benefit persisted for a decade in two of them. The secondary failure of the DPP-4i occurred in a CFRD patient with a phenotype resembling type 2 diabetes. A DPP-4i may have an important role in the management of CFRD.

PROMISE: Working with the CF community to understand emerging clinical and research needs for those treated with highly effective CFTR modulator therapy

Highly effective CFTR modulator drug therapy is increasingly available to those with cystic fibrosis. Multiple observational research studies are now being conducted to better understand the impacts of this important therapeutic milestone on long-term outcomes, patient care needs, and future research priorities. PROMISE is a large, multi-disciplinary academic study focused on the broad impacts of starting elexacaftor/tezacaftor/ivacaftor in the US population age 6 years and older. The many areas of investigation and rationale for each are discussed by organ systems, along with recognition of remaining important questions that will not be addressed by this study alone. Knowledge gained through this and multiple complementary studies around the world will help to understand important health outcomes, clinical care priorities, and research needs for a large majority of people treated with these or similarly effective medications targeting the primary cellular impairment in cystic fibrosis.

Hypoglycemia in cystic fibrosis during an extended oral glucose tolerance test

BACKGROUND

Hypoglycemia in cystic fibrosis (CF), in the absence of glucose-lowering therapies, has long been identified as an important issue in the management of CF. There is currently still no unifying hypothesis for its etiology.

AIM

The aims of this study were to perform a 3-h oral glucose tolerance test (OGTT) in participants with CF and (1) document glucose, insulin, glucagon, glucagon-like-peptide-1 (GLP-1), and glucose-dependent insulinotropic peptide (GIP) release patterns within varying glucose tolerance groups during the OGTT; (2) determine the prevalence of hypoglycemic during the OGTT; and (3) define any association between hypoglycemia and patterns of insulin, glucagon, GLP-1, and GIP release.

METHODS

Eligible participants attending an adult CF clinic completed a 3-h OGTT. Hypoglycemia on OGTT was defined as mild (glucose 3.4-3.9 mmol/L), moderate (glucose 3.1-3.3 mmol/L), and severe (glucose ≤ 3 mmol/L). Hormones were measured at fasting, 30, 60, 120, and 180 min.

RESULTS

Twenty-four participants completed the study, of which 7 had normal glucose tolerance, 12 had abnormal glucose tolerance, and 5 had cystic fibrosis related diabetes (CFRD). All participants had a delayed insulin response compared with normative data. All glucose tolerance groups showed appropriate and similar suppression of fasting glucagon. Four participants (17%) had mild hypoglycemic, three (13%) had moderate hypoglycemic, and eight (33%) had severe hypoglycemic. No participant with CFRD demonstrated hypoglycemic. Of the 19 participants without CFRD, 15 (79%) experienced hypoglycemic. Participants with hypoglycemic had greater peak glucose and insulin responses than those that did not have hypoglycemic, and this approached significance (p = .0625 for glucose and p = .0862 for insulin). No significant mean differences between GLP-1 and GIP release were found. There was no relationship between hypoglycemic and modulator therapy.

CONCLUSION

Postprandial hypoglycemic was unmasked by the extension of an OGTT to 3 h. Delayed and abnormal insulin release, and ineffective counter-regulatory action of glucagon may have a role in its etiology.

Semaglutide in Cystic Fibrosis-Related Diabetes

CONTEXT AND OBJECTIVE

In spite of the evidence that inadequately controlled glycemia is associated with worse clinical outcomes, cystic fibrosis-related diabetes (CFRD) is not well controlled in a majority of patients. The objective of this report is to demonstrate the effect of the addition of semaglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA), to basal insulin to control glycemia in one such patient.

DESIGN, INTERVENTION, AND THE MAIN OUTCOME MEASURES

The replacement of rapidly acting prandial insulin with semaglutide weekly with continuation of basal insulin. Glycated hemoglobin A1c (HbA1c) was measured and continuous glucose monitoring (CGM) was conducted.

RESULTS

There was a significant improvement in glycemic control, reduction in HbA1c from 9.1% to 6.7% and stable euglycemic pattern on CGM (mean glucose, 142 mg/dL; SD, 51) within 3 months of starting treatment. There was no increase in plasma pancreatic enzyme concentrations.

CONCLUSIONS

Semaglutide at a low dose was able to replace prandial insulin and control glycemia in combination with basal insulin.

Cystic fibrosis-related diabetes: The unmet need

Cystic fibrosis (CF) is a common autosomal recessive disease. Life expectancy of patients with CF continues to improve mainly driven by the evolving therapies for CF-related organ dysfunction. The prevalence of CF-related diabetes (CFRD) increases exponentially as patients’ age. Clinical care guidelines for CFRD from 2010, recommend insulin as the mainstay of treatment. Many patients with CFRD may not require exogenous insulin due to the heterogeneity of this clinical entity. Maintenance of euglycemia by enhancing endogenous insulin production, secretion and degradation with novel pharmacological therapies like glucagon-like peptide-1 agonist is an option that remains to be fully explored. As such, the scope of this article will focus on our perspective of glucagon-like peptide-1 receptor agonist in the context of CFRD. Other potential options such as sodium-glucose cotransporter-2 and dipeptidyl peptidase 4 inhibitors and their impact on this patient population is limited and further studies are required.

Loss of incretin effect contributes to postprandial hyperglycaemia in cystic fibrosis-related diabetes

AIM

To investigate the incretin axis in people with cystic fibrosis.

METHODS

Adults with cystic fibrosis-related diabetes, cystic fibrosis without diabetes, and controls (adults without cystic fibrosis and without diabetes) underwent an oral glucose tolerance test and then a closely matched isoglycaemic i.v. glucose infusion. On each occasion, glucose, insulin, C-peptide, total and active glucagon-like peptide-1 and gastric inhibitory polypeptide responses were recorded and incremental areas under curves were calculated for 60 and 240 min.

RESULTS

Five adults with cystic fibrosis-related diabetes, six with cystic fibrosis without diabetes and six controls, matched for age and BMI, completed the study. Glucose during oral glucose tolerance test closely matched those during isoglycaemic i.v. glucose infusion. The calculated incretin effect was similar in the control group and the cystic fibrosis without diabetes group (28% and 29%, respectively), but was lost in the cystic fibrosis-related diabetes group (cystic fibrosis-related diabetes vs control group: -6% vs 28%; p=0.03). No hyposecretion of glucagon-like peptide-1 or gastric inhibitory polypeptide was observed; conversely, 60-min incremental area under the curve for total glucagon-like peptide-1 was significantly higher in the cystic fibrosis-related diabetes group than in the control group [1070.4 (254.7) vs 694.97 (308.1); p=0.03] CONCLUSIONS: The incretin effect was lost in cystic fibrosis-related diabetes despite adequate secretion of the incretin hormones. These data support the concept that reduced incretin hormone insulinotropic activity contributes significantly to postprandial hyperglycaemia in cystic fibrosis-related diabetes.

Incretin dysfunction and hyperglycemia in cystic fibrosis: Role of acyl-ghrelin

BACKGROUND

Insulin secretion is insufficient in cystic fibrosis (CF), even before diabetes is present, though the mechanisms involved remain unclear. Acyl-ghrelin (AG) can diminish insulin secretion and is elevated in humans with CF.

METHODS

We tested the hypothesis that elevated AG contributes to reduced insulin secretion and hyperglycemia in CF ferrets.

RESULTS

Fasting AG was elevated in CF versus non-CF ferrets. Similar to its effects in other species, AG administration in non-CF ferrets acutely reduced insulin, increased growth hormone, and induced hyperglycemia. During oral glucose tolerance testing, non-CF ferrets had responsive insulin, glucagon like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) levels and maintained normal glucose levels, whereas CF ferrets had insufficient responses and became hyperglycemic. Interestingly in wild-type ferrets, the acyl-ghrelin receptor antagonist [D-Lys3]-GHRP-6 impaired glucose tolerance, and abolished insulin, GLP-1, and GIP responses during glucose tolerance testing. By contrast, in CF ferrets [D-Lys3]-GHRP-6 improved glucose tolerance, enhanced the insulin-to-glucose ratio, but did not impact the already low GLP-1 and GIP levels.

CONCLUSIONS

These results suggest a mechanism by which elevated AG contributes to CF hyperglycemia through inhibition of insulin secretion, an effect magnified by low GLP-1 and GIP. Interventions that lower ghrelin, ghrelin action, and/or raise GLP-1 or GIP might improve glycemia in CF.

Survival in a bad neighborhood: pancreatic islets in cystic fibrosis

In cystic fibrosis (CF), ductal plugging and acinar loss result in rapid decline of exocrine pancreatic function. This destructive process results in remodeled islets, with only a modest reduction in insulin producing β cells. However, β-cell function is profoundly impaired, with decreased insulin release and abnormal glucose tolerance being present even in infants with CF. Ultimately, roughly half of CF subjects develop diabetes (termed CF-related diabetes, CFRD). Importantly, CFRD increases CF morbidity and mortality via worsening catabolism and pulmonary disease. Current accepted treatment options for CFRD are aimed at insulin replacement, thereby improving glycemia as well as preventing nutritional losses and lung decline. CFRD is a unique form of diabetes with a distinct pathophysiology that is as yet incompletely understood. Recent studies highlight emerging areas of interest. First, islet inflammation and lymphocyte infiltration are common even in young children with CF and may contribute to β-cell failure. Second, controversy exists in the literature regarding the presence/importance of β-cell intrinsic functions of CFTR and its direct role in modulating insulin release. Third, loss of the CF transmembrane conductance regulator (CFTR) from pancreatic ductal epithelium, the predominant site of its synthesis, results in paracrine effects that impair insulin release. Finally, the degree of β-cell loss in CFRD does not appear sufficient to explain the deficit in insulin release. Thus, it may be possible to enhance the function of the remaining β cells using strategies such as targeting islet inflammation or ductal CFTR deficiency to effectively treat or even prevent CFRD.

Bile acid homeostasis in gastrointestinal and metabolic complications of cystic fibrosis

With the improved treatment of the pulmonary complications of cystic fibrosis (CF), gastrointestinal problems have become more important in the morbidity in CF. A hallmark of the gastrointestinal phenotype of CF, apart from pancreatic insufficiency, is a disruption of bile acid homeostasis. Bile acid homeostasis is important for many gastrointestinal processes including fat absorption, inflammation, microbial composition, as well as regulation of whole body energy metabolism. This review describes the impairment of bile acid homeostasis in CF, its possible consequences for gastrointestinal and metabolic complications and its potential as a target for therapy.

Impaired secretion of active GLP-1 in patients with hypertriglyceridaemia: A novel lipotoxicity paradigm?

BACKGROUND

Lipotoxicity plays an important role in the pathogenesis of β-cell dysfunction. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that exerts beneficial effects on the number and function of islet β cells. However, the effect of lipotoxicity on GLP-1 secretion is still unknown.

METHODS

Twenty-five patients who were newly diagnosed with diabetes were recruited from 400 subjects based on 75-g Oral Glucose Tolerance Test. Patients were divided into diabetes (DM) and DM combined with hypertriglyceridaemia (DM + HTG) groups according to their serum triglyceride (TG) levels. Seventy-one normal controls and 17 patients with isolated hypertriglyceridaemia were matched by age and gender.

RESULTS

Total and active fasting GLP-1 and 2-hour GLP-1 levels were not significantly altered among the 4 groups. However, total and active ΔGLP-1 levels (the difference between 2-hour GLP-1 and fasting GLP-1 levels) were significantly reduced in the isolated HTG, DM, and DM + HTG groups, particularly the DM + HTG group. The ratio of serum active GLP-1 (AGLP-1) to total GLP-1 (TGLP-1) levels was also decreased in patients with isolated HTG, suggesting that active GLP-1 secretion may be more seriously impaired. Both ΔTGLP-1 and ΔAGLP-1 levels were negatively correlated with serum TG levels, body mass index and fasting plasma glucose (FPG) levels and positively correlated with HDL-C levels. According to the multivariate linear regression analysis, only TG and FPG levels were independently associated with ΔTGLP-1 and ΔAGLP-1 levels.

CONCLUSION

Impaired GLP-1 secretion was associated with hypertriglyceridaemia and diabetes, and a more obvious association was noted in hypertriglyceridaemic patients with diabetes.

Cystic Fibrosis-Related Diabetes

Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasian populations. Individuals with CF have seen significant increases in life expectancy in the last 60 years. As a result, previously rare complications are now coming to light. The most common of these is cystic fibrosis-related diabetes (CFRD), which affects 40-50% of CF adults. CFRD significantly impacts the pulmonary function and longevity of CF patients, yet a lack of consensus on the best methods to diagnose and treat CFRD remains. We begin by reviewing our understanding of the pathogenesis of CFRD, as emerging evidence shows the cystic fibrosis transmembrane conductance regulator (CFTR) also has important roles in the release of insulin and glucagon and in the protection of β cells from oxidative stress. We then discuss how current recommended methods of CFRD diagnosis are not appropriate, as continuous glucose monitoring becomes more effective, practical, and cost-effective. Finally, we evaluate emerging treatments which have narrowed the mortality gap within the CF patient group. In the future, pharmacological potentiators and correctors directly targeting CFTR show huge promise for both CFRD and the wider CF patient groups.

Pulmonary Function and Sleep Breathing: Two New Targets for Type 2 Diabetes Care

Population-based studies showing the negative impact of type 2 diabetes (T2D) on lung function are overviewed. Among the well-recognized pathophysiological mechanisms, the metabolic pathways related to insulin resistance (IR), low-grade chronic inflammation, leptin resistance, microvascular damage, and autonomic neuropathy are emphasized. Histopathological changes are exposed, and findings reported from experimental models are clearly differentiated from those described in humans. The accelerated decline in pulmonary function that appears in patients with cystic fibrosis (CF) with related abnormalities of glucose tolerance and diabetes is considered as an example to further investigate the relationship between T2D and the lung. Furthermore, a possible causal link between antihyperglycemic therapies and pulmonary function is examined. T2D similarly affects breathing during sleep, becoming an independent risk factor for higher rates of sleep apnea, leading to nocturnal hypoxemia and daytime sleepiness. Therefore, the impact of T2D on sleep breathing and its influence on sleep architecture is analyzed. Finally, the effect of improving some pathophysiological mechanisms, primarily IR and inflammation, as well as the optimization of blood glucose control on sleep breathing is evaluated. In summary, the lung should be considered by those providing care for people with diabetes and raise the central issue of whether the normalization of glucose levels can improve pulmonary function and ameliorate sleep-disordered breathing. Therefore, patients with T2D should be considered a vulnerable group for pulmonary dysfunction. However, further research aimed at elucidating how to screen for the lung impairment in the population with diabetes in a cost-effective manner is needed.

CF-related diabetes: Containing the metabolic miscreant of cystic fibrosis

Cystic fibrosis-related diabetes (CFRD) is associated with both an increase in morbidity and mortality in people with cystic fibrosis (CF). With increased screening and improved life expectancy of people with CF, the prevalence of CFRD is expected to rise further. The underlying pathophysiological mechanisms causing glucose intolerance and diabetes in patients with CF are not well understood but both functional and structural abnormalities in islet cells are likely to have key roles. Insulin therapy improves health outcomes in patients with CF. Future research is needed to better understand the mechanisms underlying the development of CFRD and to develop new screening and treatment strategies to minimize the detrimental impact of CFRD on health outcomes in people with CF.

Evolving Mechanistic Views and Emerging Therapeutic Strategies for Cystic Fibrosis-Related Diabetes

Diabetes is a common and important complication of cystic fibrosis, an autosomal recessive genetic disease due to mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Cystic fibrosis-related diabetes (CFRD) is associated with profound detrimental effects on the disease course and mortality and is expected to increase in prevalence as the survival of patients with cystic fibrosis continues to improve. Despite progress in the functional characterization of CFTR molecular defects, the mechanistic basis of CFRD is not well understood, in part because of the relative inaccessibility of the pancreatic tissue and the limited availability of representative animal models. This review presents a concise overview of the current understanding of CFRD pathogenesis and provides a cutting-edge update on novel findings from human and animal studies. Potential contributions from paracrine mechanisms and β-cell compensatory mechanisms are highlighted, as well as functional β-cell and α-cell defects, incretin defects, exocrine pancreatic insufficiency, and loss of islet cell mass. State-of-the-art and emerging treatment options are explored, including advances in insulin administration, CFTR modulators, cell replacement, gene replacement, and gene editing therapies.

A Practical Approach to Glucose Abnormalities in Cystic Fibrosis

Cystic fibrosis is a common genetic condition and abnormal glucose handling leading to cystic fibrosis-related diabetes (CFRD) is a frequent comorbidity. CFRD is mainly thought to be the result of progressive pancreatic damage resulting in beta cell dysfunction and loss of insulin secretion. Whilst Oral Glucose Tolerance Testing is still recommended for diagnosing CFRD, the relationship between glucose abnormalities and adverse outcomes in CF is complex and occurs at stages of dysglycaemia occurring prior to diagnosis of diabetes by World Health Organisation criteria. Insulin remains the mainstay of treatment of CF-related glucose abnormalities but the timing of insulin commencement, optimum insulin regime and targets of glycaemic control are not clear. These complexities are compounded by common issues with nutritional status, need for enteral feeding, steroid use and high disease burden on CF patients.

Cystic Fibrosis-Related Diabetes in Children: An Update

Cystic fibrosis-related diabetes mellitus (CFRD) is the most common endocrine complication of cystic fibrosis (CF), affecting more than 50% of patients by the 4th decade of life. CFRD is often preceded by worsening pulmonary status and nutritional decline. Treatment of CFRD is associated with improvements in body weight and pulmonary function and a reduction in pulmonary exacerbations. Because of the clinical significance of CFRD, diabetes screening with an oral glucose tolerance test (OGTT) is recommended annually for all patients with CF starting at age 10 years. The OGTT detects CFRD with greater sensitivity than random glucose or hemoglobin A1c testing. The first-line treatment for CFRD is insulin. The use of other treatments such as oral medications remains under study. [Pediatr Ann. 2016;45(9):e321-e326.].

Cystic Fibrosis Related Diabetes: a Unique Challenge in Diabetes Care

Cystic Fibrosis (CF) is a common autosomal recessive disease that affects multiple organs due to a defect in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). This transporter is present in various organs and tissues, including the airway epithelium, sinuses, pancreas, intestine, biliary tree, the vas deferens, and the sweat ducts, making CF a multi-system disease1. As CF patients are living longer, pancreatic function declines and diabetes emerges, further complicating the nutritional status and care of these patients.

Pancreatic enzyme supplementation improves the incretin hormone response and attenuates postprandial glycemia in adolescents with cystic fibrosis: a randomized crossover trial

CONTEXT

Cystic fibrosis-related diabetes is characterized by postprandial, rather than fasting, hyperglycemia. Gastric emptying and the release of the incretin hormones [glucagon-like peptide-1 (GLP-1) and glucose dependent insulinotropic polypeptide (GIP)] are central to postprandial glycemic control. Lipolysis is required for fat to slow gastric emptying and stimulate incretin release.

OBJECTIVE

We aimed to determine the effect of pancreatic enzyme replacement therapy (PERT) on postprandial glycemia in adolescents with cystic fibrosis (CF).

DESIGN

This was a double-blinded randomized crossover trial. Subjects consumed a high-fat pancake, with either PERT (50 000 IU lipase) or placebo. Gastric emptying was measured by a breath test and blood sampled frequently for plasma blood glucose, insulin, glucagon, GLP-1, and GIP. Data were also compared with seven healthy subjects.

PARTICIPANTS

Fourteen adolescents (13.1 ± 2.7 y) with pancreatic-insufficient CF and seven healthy age-matched controls participated in the study.

MAIN OUTCOME MEASURE

Postprandial hyperglycemia was measured as peak glucose and area under the curve for blood glucose at 240 minutes.

RESULTS

CF subjects had postprandial hyperglycemia compared with controls (area under the curve, P < .0001). PERT reduced postprandial hyperglycemia (P = .0002), slowed gastric emptying (P = .003), and normalized GLP-1 and GIP secretion (P < .001 for each) when compared with placebo, without affecting insulin.

CONCLUSION

In young people with pancreatic insufficient CF, PERT markedly attenuates postprandial hyperglycemia by slowing gastric emptying and augmenting incretin hormone secretion.

The clinical significance of the gut microbiota in cystic fibrosis and the potential for dietary therapies

Cystic fibrosis (CF) is characterised by many comorbidities related to aberrant mucosa and chronic inflammation in the respiratory and digestive systems. The intestinal mucosa serves as the primary interface between the gut microbiota and endocrine, neural and immune systems. There is emerging evidence that aberrant intestinal mucosa in CF may associate with an altered gut microbiota. Compared to healthy subjects, the overall bacterial abundance and species richness seems to be reduced in CF, accompanied by a trend in suppression of Firmicutes and Bacteroidetes spp. and an augmentation of potentially pathogenic species. There is also some concordance of gut and respiratory microbiotas in CF infants over time. The clinical significance of these observations awaits investigation. The gut microbiota have some potential in CF management by affecting inflammatory and immune responses, and influencing aberrant mucosa. As an important modifiable factor, diet therapies such as probiotics and prebiotics have shown initial promise in improving CF related conditions associated with chronic inflammation. More studies are needed to confirm this, as well as the efficacy of other dietary strategies such as modulating dietary fat and indigestible carbohydrate. Similarly, dietary modification of gut microbiota to optimise nutritional status in CF may be feasible, although more CF-specific studies are warranted.

Quantifying insulin sensitivity and entero-insular responsiveness to hyper- and hypoglycemia in ferrets

Ferrets are an important emerging model of cystic fibrosis related diabetes. However, there is little documented experience in the use of advanced techniques to quantify aspects of diabetes pathophysiology in the ferret. Glycemic clamps are the gold standard technique to assess both insulin sensitivity and insulin secretion in humans and animal models of diabetes. We therefore sought to develop techniques for glycemic clamps in ferrets. To assess insulin sensitivity, we performed euglycemic hyperinsulinemic clamps in 5–6 week old ferrets in the anesthetized and conscious states. To assess insulin secretion, we performed hyperglycemic clamps in conscious ferrets. To evaluate responsiveness of ferret islet and entero-insular hormones to low glucose, a portion of the hyperglycemic clamps were followed by a hypoglycemic clamp. The euglycemic hyperinsulinemic clamps demonstrated insulin responsiveness in ferrets similar to that previously observed in humans and rats. The anesthetic isoflurane induced marked insulin resistance, whereas lipid emulsion induced mild insulin resistance. In conscious ferrets, glucose appearance was largely suppressed at 4 mU/kg/min insulin infusion, whereas glucose disposal was progressively increased at 4 and 20 mU/kg/min insulin. Hyperglycemic clamp induced first phase insulin secretion. Hypoglycemia induced a rapid diminishment of insulin, as well as a rise in glucagon and pancreatic polypeptide levels. The incretins GLP-1 and GIP were affected minimally by hyperglycemic and hypoglycemic clamp. These techniques will prove useful in better defining the pathophysiology in ferrets with cystic fibrosis related diabetes.

Effect of diabetes mellitus on pharmacokinetic and pharmacodynamic properties of drugs

The effects of diabetes mellitus on the pharmacokinetics and pharmacodynamics of drugs have been well described in experimental animal models; however, only minimal data exist for humans and the current knowledge regarding the effects of diabetes on these properties remains unclear. Nevertheless, it has been observed that the pharmacokinetics and pharmacodynamics of drugs are changed in subjects with diabetes. It has been reported that diabetes may affect the pharmacokinetics of various drugs by affecting (i) absorption, due to changes in subcutaneous adipose blood flow, muscle blood flow and gastric emptying; (ii) distribution, due to non-enzymatic glycation of albumin; (iii) biotransformation, due to regulation of enzymes/transporters involved in drug biotransformation; and (iv) excretion, due to nephropathy. Previously published data also suggest that diabetes-mediated changes in the pharmacokinetics of a particular drug cannot be translated to others. Although clinical studies exploring the effect of diabetes on pharmacodynamics are still very limited, there is evidence that disease-mediated effects are not limited only to pharmacokinetics but also alter pharmacodynamics. However, for many drugs it remains unclear whether these influences reflect diabetes-mediated changes in pharmacokinetics rather than pharmacodynamics. In addition, even though diabetes-mediated pharmacokinetics and pharmacodynamics might be anticipated, it is important to study the effect on each drug and not generalize from observed data. The available data indicate that there is a significant variability in drug response in diabetic subjects. The discrepancies between individual clinical studies as well as between ex vivo and clinical studies are probably due to (i) the restricted and focused population of subjects in clinical studies; (ii) failure to consider type, severity and duration of the disease; (iii) histopathological characteristics generally being missing; and (iv) other factors such as varying medication use, dietary protein intake, age, sex and obesity. The obesity epidemic in the developed world has also inadvertently influenced the directions of pharmacological research. This review attempts to map new information gained since Gwilt published his paper in Clinical Pharmacokinetics in 1991. Although a large body of research has been conducted and significant progress has been made, we still have to conclude that the available information regarding the effect of diabetes on pharmacokinetics and pharmacodynamics remains unclear and further clinical studies are required before we can understand the clinical significance of the effect. An understanding of diabetes-mediated changes as well as of the source of the variability should lead to the improvement of the medical management and clinical outcomes in patients with this widespread disease.