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The link between cardiac autonomic neuropathy and risk of cardiovascular disease is highlighted as an area in which research is needed. This study was undertaken to evaluate the association between measures of cardiac autonomic function and cardiac vascular function in type 1 diabetes using new and sensitive methods. This was a cross-sectional study in patients with type 1 diabetes, stratified by normoalbuminuria (n = 30) and macroalbuminuria (n = 30), and in healthy control subjects (n = 30). Cardiac autonomic function was evaluated using heart rate variability (HRV) indices, cardiovascular autonomic reflex tests (CARTs), and cardiac 123I-metaiodobenzylguanidine (MIBG) imaging. Cardiac vascular function was assessed as myocardial flow reserve (MFR) measured by cardiac 82Rb-positron emission tomography/computed tomography. The measures of cardiac autonomic function (except low frequency–to–high frequency ratio and the Valsalva test ratio) were positively correlated to MFR in unadjusted analysis. All the HRV indices lost significance after adjustment for age and heart rate. After further adjustment for relevant cardiovascular risk factors, the late heart-to-mediastinum ratio directly measuring the function of adrenergic receptors and sympathetic integrity (from the MIBG scintigraphy) and the 30-to-15 ratio (a CART), remained positively associated with MFR (P ≤ 0.04). Cardiac autonomic dysfunction, including loss of cardiac sympathetic integrity in type 1 diabetes, is associated with and may contribute to impaired myocardial blood flow regulation.

Sodium-glucose cotransporter-2 (SGLT2) inhibition is emerging as a beneficial adjunctive therapy in type 1 diabetes (T1D). It is hypothesized that SGLT2 inhibition relieves hypoxia in the kidneys. As mitochondrial dysfunction might contribute to kidney hypoxia, SGLT2 inhibition could ameliorate hypoxia via restored mitochondrial respiration. Changes in metabolic processes in peripheral blood mononuclear cells (PBMCs) are associated with various diseases including diabetes. PBMCs are an easily accessible reporter cell population to test changes in cellular metabolism caused by changes in blood glucose. The aim of this study was to investigate the effects of a single dose of 50 mg dapagliflozin compared to placebo on PBMCs’ bioenergetics in individuals with T1D in a double blinded randomized crossover study with a two-week washout period. With Seahorse extracellular flux technology, we analysed the efficiency of mitochondrial oxidative phosphorylation and glycolysis in PBMCs obtained from a fresh blood sample of each study participant before and after intervention. Fifteen individuals (33% females) with mean (±SD) age 58 (±14) years and Hba1c 8.0 (±0.6) % were included. Dapagliflozin did not influence PBMC mitochondrial oxidative phosphorylation. However, dapagliflozin significantly improved PBMC glycolytic reserve by 35% (mean ±SE, 3.5 ±0.3 e-6 ECAR/cell number) compared to baseline (2.6 ±0.5 e-6 ECAR/cell number). Our results suggest that dapagliflozin enhances PBMCs’ flexibility to use glycolysis as an energy supply pathway in individuals with T1D. This study advances our mechanistic understanding of the subtle changes in systemic metabolism and the beneficial effects at the cellular level of SGLT2 inhibition in patients with T1D. Disclosure J. Melo: None. J. Laursen: None. N. S. Heinrich: Stock/Shareholder; Self; Akebia Therapeutics, Inc., Novo Nordisk A/S. I. B. Rasmussen: None. C. S. Hansen: None. M. Frimodt-moeller: None. P. Rossing: Advisory Panel; Self; Astellas Pharma Inc., AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Gilead Sciences, Inc., Merck KGaA, Merck Sharp & Dohme Corp., Novo Nordisk A/S, Sanofi, Vifor Pharma Management Ltd. J. Størling: None.

Objective: Inhibitors of the sodium-glucose cotransporter 2 slow the progression of diabetic kidney disease, possibly by reducing the proximal tubule transport workload with subsequent improvement of renal oxygenation. We aimed to test this hypothesis in individuals with type 1 diabetes and albuminuria. Research Design and Methods: A randomized, double-blinded, crossover study with a single dose of 50 mg dapagliflozin and placebo separated by a two-week washout period. Magnetic resonance imaging (MRI) was used to assess renal tissue oxygenation (R2*), renal perfusion (arterial spin labelling) and renal artery flow (phase contrast imaging) at baseline and three and six hours from intervention. Exploratory outcomes, including baroreflex sensitivity, peripheral blood oxygen saturation and peripheral blood mononuclear mitochondrial oxygen consumption rate, were evaluated at baseline and 12 hours from intervention. Results: We included 15 individuals (33% females) with a mean (±SD) age 58±14 years, median [Q1;Q3] urinary albumin creatinine ratio of 46 [21;58] mg/g and eGFR of 73±32 ml/min/1.73m2. The mean changes (±SE) in renal cortical R2* from baseline to six hours were for dapagliflozin -1.3±0.7 s-1 and for placebo +1.4±0.7 s-1 respectively, resulting in a difference between interventions of -2.6 s-1 (95% CI, -4.5 to -0.7, p=0.001). No between-intervention differences were found in other MRI outcomes, physiological parameters or exploratory outcomes. Conclusions: Dapagliflozin improved renal cortical R2* without changing renal perfusion and blood flow. This suggests an improved renal cortical oxygenation due to reduced tubular transport work in the proximal tubules. Disclosure J. Laursen: None. P. Groop: Advisory Panel; Self; AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Merck Sharp & Dohme Corp., Speaker’s Bureau; Self; Boehringer Ingelheim International GmbH, Mundipharma International. M. Frimodt-moeller: None. U. B. Andersen: Other Relationship; Self; Bayer AG. P. Rossing: Advisory Panel; Self; Astellas Pharma Inc., AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Gilead Sciences, Inc., Merck KGaA, Merck Sharp & Dohme Corp., Novo Nordisk A/S, Sanofi, Vifor Pharma Management Ltd. N. S. Heinrich: Stock/Shareholder; Self; Akebia Therapeutics, Inc., Novo Nordisk A/S. J. Melo: None. B. Haddock: None. I. B. Rasmussen: None. F. Safavimanesh: None. C. S. Hansen: None. J. Størling: None. H. B. W. Larsson: None.

Cardiac autonomic dysfunction and cardiac microvascular dysfunction are diabetic complications associated with increased mortality, but the association between these has been difficult to assess. We applied new and sensitive methods to assess this in patients with type 2 diabetes mellitus (T2DM). In a cross-sectional design, coronary flow reserve (CFR) assessed by cardiac 82Rb-positron emission tomography/computed tomography, cardiac autonomic reflex tests, and heart rate variability indices were performed in 55 patients with T2DM, without cardiovascular disease, and in 28 control subjects. Cardiac 123I-metaiodobenzylguanidine scintigraphy was conducted in a subgroup of 29 patients and 14 control subjects and evaluated as the late heart-to-mediastinum ratio and washout rate. Impaired function of all the cardiac autonomic measures (except the washout rate) was associated with reduced CFR. A heart rate variability index, reflecting sympathetic and parasympathetic function (low-frequency power), and the late heart-to-mediastinum ratio, reflecting the function of adrenergic receptors and sympathetic activity, were positively correlated with CFR after adjustment for age and heart rate. The late heart-to- mediastinum ratio remained correlated with CFR after further adjustment. In patients with T2DM without cardiovascular disease, we demonstrate an independent association between cardiac autonomic function and CFR. We suggest that a reduced cardiac autonomic function and damage to the adrenergic receptors may contribute to the development of cardiac microvascular dysfunction.