Regression of Left Ventricular Hypertrophy in Diabetic Nephropathy: Loss of Parasympathetic Function Predicts Response to Treatment

The Diabetic Cardiorenal Nexus

The end-stage of the clinical combination of heart failure and kidney disease has become known as cardiorenal syndrome. Adverse consequences related to diabetes, hyperlipidemia, obesity, hypertension and renal impairment on cardiovascular function, morbidity and mortality are well known. Guidelines for the treatment of these risk factors have led to the improved prognosis of patients with coronary artery disease and reduced ejection fraction. Heart failure hospital admissions and readmission often occur, however, in the presence of metabolic, renal dysfunction and relatively preserved systolic function. In this domain, few advances have been described. Diabetes, kidney and cardiac dysfunction act synergistically to magnify healthcare costs. Current therapy relies on improving hemodynamic factors destructive to both the heart and kidney. We consider that additional hemodynamic solutions may be limited without the use of animal models focusing on the cardiomyocyte, nephron and extracellular matrices. We review herein potential common pathophysiologic targets for treatment to prevent and ameliorate this syndrome.

Does empagliflozin modulate the autonomic nervous system among individuals with type 2 diabetes and coronary artery disease? The EMPA-HEART CardioLink-6 Holter analysis

Context

We examined if empagliflozin was associated with modulation of cardiac autonomic tone among subjects with type 2 diabetes and stable coronary artery disease (CAD) relative to placebo.

Methods

Using ambulatory 24-h Holter electrocardiographic data prospectively collected from a randomized trial, we compared changes in heart rate variability (HRV) parameters between empagliflozin- and placebo-assigned subjects over a follow-up period of 6 months. Measured HRV domains included: standard deviation (SD) of NN intervals (SDNN), SD of average NN intervals per 5-min (SDANN), root mean square of successive RR interval differences (RMSSD), % successive NN intervals differing >50 ms (ms) (pNN50), low frequency (LF), high frequency (HF) and the LF/HF ratio (LF:HF). Differences in HRV parameters between the 2 groups were compared with analysis of covariance (ANCOVA). Statistical measures of significance were reported as adjusted differences between the 2 groups and their corresponding 95% confidence intervals.

Results

Sixty-six subjects completed 24-h Holter monitoring at baseline and 6-months. Over 6 months, the change in HRV was similar between subjects treated with empagliflozin vs. placebo for the following parameters: RMSSD -1.2 ms (-6.0 to 3.6 ms); pNN50 0.5% (-2.6 to 3.6%); VLF -907.8 ms² (-2388.8 to 573.1 ms²); LF -341 ms² (-878.7 to 196.7 ms²); HF -33.8 ms² (-111.1 to 43.5 ms²); LF:HF -0.1 (-0.4 to 0.2). Subjects who received placebo experienced an increase in SDNN 18.6 ms (2.8–34.3 ms) and SDANN 20.2 ms (3.2–37.3 ms) relative to those treated with empagliflozin.

Conclusion

Compared to placebo, empagliflozin did not result in changes in autonomic tone among individuals with type 2 diabetes and stable coronary artery disease.

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Sodium-glucose cotransporter-2 (SGLT2) inhibitors’ mechanism of cardiovascular benefit is unknown.

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Impaired autonomic tone is associated with adverse cardiac events.

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Cardiac autonomic tone was assessed with Holter studies from a randomized trial.

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Similar autonomic tone noted between subjects treated with empagliflozin and placebo.

Pulsatile intermittent intravenous insulin therapy for attenuation of retinopathy and nephropathy in type 1 diabetes mellitus

Many hormones are secreted in a pulsatile fashion that is more efficient than continuous secretion when tested in vivo. A trial of multiple daily insulin doses with or without the addition of weekly pulsatile insulin infusion therapy was designed to determine if deterioration of renal and retinal function could be blunted. Sixty-five study subjects were evaluated prospectively in 7 centers. Thirty-six patients were randomly allocated to the infusion group and 29 to the standard therapy group. Mean serum creatinine was 1.6 mg/dL in both groups. Subjects were excluded if clearance was less than 30 mL/min. There were no significant differences between the groups with respect to age, duration of diabetes, sex distribution, glycohemoglobin, blood pressure, angiotensin-converting enzyme inhibitor use, proteinuria, or baseline diabetic retinopathy (DR) severity level (all eyes exhibited DR; 8 were deemed technically not amenable to evaluation). Progression of DR was noted in 31.6% of 57 patients (32.3% treated, 30.8% control; P = 1.0) with both eyes evaluable. For patients with 12 or more months of follow-up, 27.9% of 43 patients demonstrated progression of DR (32.0% treated, 22.2% control; P = .57). There were no significant differences between study groups with respect to progression or marked progression, nor was there any influence of duration of follow-up. Progression of DR was noted in 18.8% of 122 eyes that could be adequately evaluated (17.9% of 67 treated, 20% of 55 controls; P = .39). Serum creatinine increased to 1.7 mg/dL in the treatment group and to 1.9 mg/dL in the control group (P = .03). Statistically significant preservation of renal function by pulsatile insulin infusion was not matched by a statistically significant prevention of DR progression compared with standard diabetes care. Inadequate statistical power or duration of the study, or lack of further benefit of pulsatile insulin infusion on the retina in the presence of angiotensin-converting enzyme inhibition may be responsible.

Utilization of an abbreviated diabetes impact management scale to assess change in subjective disability during a trial of pulsatile insulin delivery demonstrates benefit

A prospective interventional study of pulsatile intravenous insulin infusion therapy has demonstrated reduction of left ventricular mass and blunting of progression of diabetic nephropathy. We anticipated that improvements in objective parameters would be associated with similar improvement measurable by the self-administered Diabetes Impact Management Scale (DIMS). The DIMS was administered at baseline and 12 months for 19 participants randomized to receive either standard insulin treatment of 3 to 4 injections of insulin daily or insulin treatment plus an additional day per week of 3 intravenous pulses over an 8-hour period. For standard vs pulsed intravenous insulin therapy, mean baseline scores were similar for the 12 total questions as well as the groups of 7 questions with emotional content and 5 with physical (neurologic) content. Mean study group scores at 1 year and changes over 1 year were not significantly different for the 7 questions with emotional content (P = .3143, .7574). Score results for the 5 questions related to neurologic status at 1 year and changes over 1 year were significantly different between patients with standard and with pulsed insulin therapy (P = .0144, 0.0004). Pulsatile intravenous insulin, when added to standard multiple-dose insulin therapy, was demonstrated to improve subjective perception of neurologic disability on repeated use of an abbreviated form of the DIMS.

A pilot study to assess utility of changes in elements of the Diabetes Impact Management Scale in evaluating diabetic patients for progressive nephropathy

A prospective study involving the use of the Diabetes Impact Management Scale (DIMS) in individuals with diabetic nephropathy as part of an interventional study of pulsatile intravenous insulin infusion therapy is used to define the utility of repeated subjective DIMS testing. We hypothesized that repeated use of such an evaluation would correlate well with other objective end points. The DIMS was administered at baseline and 12 months for 19 participants randomized to receive either standard insulin treatment of 3 to 4 injections of insulin daily or standard insulin treatment plus an additional day per week of 3 intravenous pulses over an 8-hour period. Measures of glycemic control, renal function, hemostatic factors, hemodynamics, left ventricular mass, and function were assessed at baseline and 12 months. Of 44 questions on impact of diabetes management, only 12 (5 reflecting physical and 7 reflecting emotional status) showed significant change from baseline to 1 year. Changes in the 5 physical questions related to neurologic status correlated with stable creatinine (P = .0001), stable creatinine clearance (P = .0001), and decrease in left ventricular hypertrophy (P =.0117). Repeated use of an abbreviated, standardized subjective instrument uncovered changes in quality of life that correlated with differences in renal function and left ventricular mass over 12 months. Further use of such an instrument may help us focus treatment for maximum impact.

A pilot study to test the effect of pulsatile insulin infusion on cardiovascular mechanisms that might contribute to attenuation of renal compromise in type 1 diabetes mellitus patients with proteinuria

We hypothesized that correction of insulin deficiency by pulsatile intravenous insulin infusion in type 1 diabetes mellitus patients with nephropathy preserves renal function by mechanisms involving cardiac autonomic function, cardiac mass, or efficiency, or by hemostatic mechanisms. The control group (8 patients) received subcutaneous insulin (3-4 injections per day). The intravenous infusion group (10 patients) received three 1-hour courses of pulsed intravenous insulin infusion on a single day per week in addition to subcutaneous insulin. Laboratory measurements included 2-dimensional Doppler echocardiography, 24-hour ambulatory monitoring with heart rate variation analysis, platelet aggregation and adhesion, plasma fibrinogen, factor VII, von Willebrand factor, fibrinolytic activity, plasminogen activator inhibitor, and viscosity measured at baseline and 12 months. Blood pressure control was maintained preferentially with angiotensin-converting enzyme inhibitors. Ratio of carbon dioxide production to oxygen utilization was measured with each infusion and showed rapid increase from 0.8 to 0.9 (P = .005) at weekly treatments through 12 months. We observed an annualized decrease in creatinine clearance of 9.6 mL/min for controls vs 3.0 mL/min for infusion patients. Annualized fall in blood hemoglobin was 1.9 vs 0.8 g/dL, respectively (P = .013). There were no differences between the control and infusion group with respect to glycohemoglobin, advanced glycated end products, cholesterol, or triglycerides. No differences between the study groups for hemodynamic or hemostatic factors were evident. Blood pressures were not significantly different at baseline or 12 months. We conclude that although preservation of renal function with attenuation of loss of blood hemoglobin during 12 months of intravenous insulin infusion was associated with improvement in the efficiency of fuel oxidation as measured by respiratory quotient, this occurred without differences in metabolic/hemostatic factors, cardiac autonomic function, cardiac wall, or chamber size. Our hypothesis that preservation of renal function in type 1 diabetes mellitus patients with proteinuria by weekly pulsed insulin infusion involves mechanisms from the autonomic nervous system, cardiac size, and function, or elements of hemostasis was not confirmed.