Glucose time in range and peripheral neuropathy in type 2 diabetes mellitus and chronic kidney disease

​OBJECTIVE: Compared with hemoglobin A1c (HbA1c), continuous glucose monitoring (CGM) may better capture risk of diabetes complications in patients with chronic kidney disease (CKD), including diabetic peripheral neuropathy (DPN). We hypothesized that glucose time in range (TIR), measured by CGM, is associated with DPN symptoms among participants with type 2 diabetes mellitus (type 2 DM) and moderate-to-severe CKD. ​RESEARCH DESIGN AND METHODS: We enrolled 105 people with type 2 DM treated with insulin or sulfonylurea, 81 participants with CKD (estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m²) and 24 matched control participants with eGFR ≥60 mL/min/1.73 m². Each participant wore a CGM for two 6-day periods. Calculated glycemic measures included TIR (glucose 70-180 mg/dL) and glucose management indicator (GMI). DPN symptoms were assessed using the Michigan Neuropathy Screening Instrument (MNSI) questionnaire, with a positive MNSI score defined as ≥2 symptoms. ​RESULTS: Participants with CKD had a mean age of 68 years, diabetes duration 20 years, eGFR 38 mL/min/1.73 m² and HbA1c 7.8%, 61 mmol/mol. Sixty-two participants reported ≥2 DPN symptoms, 51 (63%) with CKD and 11 (46%) controls. Less TIR and higher GMI were associated with higher risk of MNSI questionnaire score ≥2 (OR 1.25 (95% CI 1.02 to 1.52) per 10% lower TIR, and OR 1.79 (95% CI 1.05 to 3.04) per 1% higher GMI, adjusting for age, gender and race). Similar results were observed when analyses were restricted to participants with CKD. In contrast, there was no significant association of HbA1c with DPN symptoms. ​CONCLUSIONS: Symptoms of DPN were common among participants with long-standing type 2 DM and CKD. Lower TIR and higher GMI were associated with DPN symptoms.

Hypoglycemia in People with Type 2 Diabetes and CKD

BACKGROUND AND OBJECTIVES

Among people with diabetes mellitus, CKD may promote hypoglycemia through altered clearance of glucose-lowering medications, decreased kidney gluconeogenesis, and blunted counter-regulatory response. We conducted a prospective observational study of hypoglycemia among 105 individuals with type 2 diabetes treated with insulin or a sulfonylurea using continuous glucose monitors.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

We enrolled 81 participants with CKD, defined as eGFR<60 ml/min per 1.73 m², and 24 control participants with eGFR≥60 ml/min per 1.73 m² frequency-matched on age, duration of diabetes, hemoglobin A1c, and glucose-lowering medications. Each participant wore a continuous glucose monitor for two 6-day periods. We examined rates of sustained level 1 hypoglycemia (<70 mg/dl) and level 2 hypoglycemia (<54 mg/dl) among participants with CKD. We then tested differences compared with control participants as well as a second control population (n=73) using Poisson and linear regression, adjusting for age, sex, and race.

RESULTS

Over 890 total days of continuous glucose monitoring, participants with CKD were observed to have 255 episodes of level 1 hypoglycemia, of which 68 episodes reached level 2 hypoglycemia. Median rate of hypoglycemic episodes was 5.3 (interquartile range, 0.0-11.7) per 30 days and mean time spent in hypoglycemia was 28 (SD 37) minutes per day. Hemoglobin A1c and the glucose management indicator were the main clinical correlates of time in hypoglycemia (adjusted differences 6 [95% confidence interval, 2 to 10] and 13 [95% confidence interval, 7 to 20] fewer minutes per day per 1% higher hemoglobin A1c or glucose management indicator, respectively). Compared with control populations, participants with CKD were not observed to have significant differences in time in hypoglycemia (adjusted differences 4 [95% confidence interval, -12 to 20] and -12 [95% confidence interval, -29 to 5] minutes per day).

CONCLUSIONS

Among people with type 2 diabetes and moderate to severe CKD, hypoglycemia was common, particularly with tighter glycemic control, but not significantly different from groups with similar clinical characteristics and preserved eGFR.

An unusual manifestation of olfactory neuroblastoma

A 62-year-old woman presented with an 11-month history of worsening nasal symptoms of rhinorrhoea, anosmia, nasal congestion and intermittent epistaxis. MRI revealed a large mass in the upper nasal vault. Biopsy of the mass revealed an olfactory neuroblastoma. While waiting resection, she acutely developed severe proximal muscle weakness, lethargy and lower extremity oedema. Blood glucose was elevated, and hypokalaemic metabolic alkalosis was noted. Elevated serum cortisol level of 95.7 µg/dL (8.7-22.4 µg/dL) and markedly elevated 24-hour urinary cortisol level of 6962.3 µg/24 hours (4.0-50.0 µg/24 hours) with concurrent adrenocorticotropic hormone (ACTH) level of 171 pg/mL (6-58 pg/mL) were suggestive of an ACTH-dependent source of hypercortisolism. A subsequent positive high-dose dexamethasone suppression test was consistent with ectopic ACTH production. She underwent near-total resection of the right nasal mass followed by radiotherapy, resulting in complete resolution of signs and symptoms of cortisol excess.

Effects of Vitamin D2 Supplementation on Vitamin D3 Metabolism in Health and CKD

BACKGROUND AND OBJECTIVES

Vitamin D supplements are prescribed to correct low circulating concentrations of 25-hydroxyvitamin D. In CKD, vitamin D metabolism is complicated by decreased conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by CYP27B1 and possibly decreased conversion of 25-hydroxyvitamin D to 24,25-dihydroxyvitamin D by CYP24A1. The aim of this study was to determine the effects of vitamin D2 supplementation on vitamin D metabolism in health and CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a treatment-only intervention study of 25 individuals with CKD (eGFR<60 ml/min per 1.73 m2) and 44 individuals without CKD from three academic centers, all with screening 25-hydroxyvitamin D <30 ng/ml. Each participant was prescribed vitamin D2 (ergocalciferol) 50,000 IU orally twice weekly for 5 weeks. We tested whether changes in plasma concentrations of vitamin D metabolites and vitamin D metabolic ratios differed by CKD status. Plasma 1,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio and 24,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio were calculated as estimates of CYP27B1 and CYP24A1 function, respectively.

RESULTS

With treatment, plasma 25-hydroxyvitamin D2 and total 25-hydroxyvitamin D concentrations increased similarly for participants with and without CKD. For participants without CKD, 1,25-dihydroxyvitamin D2 increased (2.8±1.3-32.9±1.4 pg/ml), whereas 1,25-dihydroxyvitamin D3 decreased (45.6±1.9-14.6±1.9 pg/ml), resulting in no significant change in total 1,25-dihydroxyvitamin D; 1,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio decreased (3.0±0.2-1.7±0.2 pg/ng), and 24,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio increased (115.7±7.8-195.2±7.9 pg/ng). Individuals with CKD had lower baseline levels and smaller changes in magnitude for 1,25-dihydroxyvitamin D2 (2.1±1.6-24.4±1.6 pg/ml; P interaction =0.01), 1,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio (1.8±0.2-1.1±0.2 pg/ng; P interaction =0.05), and 24,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio (72.0±9.1-110.3±9.3 pg/ng; P interaction <0.001). Fibroblast growth factor-23 and parathyroid hormone were not significantly changed in either group.

CONCLUSIONS

Vitamin D2 supplementation decreases conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3 and induces vitamin D3 catabolism as evidenced by changes in D3 metabolites and vitamin D metabolic ratios. These effects occur without significant changes in fibroblast growth factor-23 or parathyroid hormone and are blunted in CKD.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2017_08_02_CJASNPodcast_17_09.mp3.