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TOPLINE:

Protein and carbohydrate–based insulin dosing doesn't improve glycemic control compared with carbohydrate-based dosing alone in people with type 1 diabetes (T1D).

METHODOLOGY:

• Postprandial glycemic control in people with T1D following carbohydrate-restricted diets can be challenging.
• Researchers assessed the effect of additional bolus insulin using a carbohydrate and protein–based insulin dosing on glycemic control in participants with T1D.
• Participants were randomly assigned (1:1) to either a carbohydrate and protein–based or carbohydrate-based insulin dosing (control group) alone for 12 weeks, with all following a carbohydrate-restricted diet (50-100 g/d).
• Participants in the intervention group self-administered mealtime bolus insulin based on their insulin-to-carbohydrate ratio (ICR) and an additional amount using the insulin-to-protein ratio (IPR), whereas the control group used only their ICR.
• The primary outcome was A1c levels at 12 weeks, and secondary outcomes were glycemic variability, mean blood glucose, and time spent in range (4.0-10.0 mmol/L) and in the hyperglycemic (> 10 mmol/L) and hypoglycemic (< 4.0 mmol/L) range.

TAKEAWAY:

• Investigators enrolled 34 adult participants (mean age, 39.2 years; 64.7% women; mean duration of diabetes, 20.6 years).
• At 12 weeks, the use of a carbohydrate and protein–based insulin dosing did not lead to greater improvement in A1c levels compared with the use of a carbohydrate-based insulin dosing alone (P = .65).
• Additional protein-based insulin dosing improved glycemic variability (P = .048), however, after adjusting for multiple comparisons, the results were not significant.
• Mean blood glucose, time spent in range, and time spent in hyperglycemia or hypoglycemia weren't different between the two groups.
• Many participants in the carbohydrate and protein–based dosing group reported that having to count proteins in addition to carbohydrates caused inconvenience, stress, or anxiety.

IN PRACTICE:

"Investigating the use of an IPR in addition to an ICR in people with higher baseline A1c would be of great interest, and in this study, a higher inclusion A1c would have been preferable. The difference observed in glycemic variability using an additional IPR suggests a potential clinical benefit," the authors wrote. 

SOURCE:

The study was led by Rosemary M. Hall, Department of Medicine, University of Otago, Wellington, New Zealand, and published online in the Journal of Diabetes and its Complications. 

LIMITATIONS:

The sample size was relatively small, which could have affected the power of the study. Lower baseline A1c levels than used for the study's power calculation may have overestimated the anticipated effect size. There was a significant difference in diabetes duration between the randomized groups, which potentially confounded the study results.

DISCLOSURES:

The study was supported by the Maurice and Phyllis Paykel Trust and Wellington Medical Research Foundation. The authors declared no conflicts of interest.