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In a recent study published in Journal of Clinical Endocrinology and MetabolismA group of researchers evaluated the effects of a eucaloric carbohydrate restriction (CR) diet on beta (β) cell (insulin-producing pancreatic cells) responses to glucose in adults with type 2 diabetes (T2D) (due to chronic hyperglycemia). ). (insulin resistance) compared with a high carbohydrate (HC) diet.
β-cell failure and insulin resistance, along with decreased phase 1 insulin secretion, which plays a key role in glycemic control, contribute to the development and progression of T2D. Insufficient first-step responses lead to increased levels of glucose and insulin, leading to complications such as glycosylation (binding of sugars to proteins or lipids) and lipid abnormalities. Existing T2D treatment drugs do not stimulate the secretion of the first phase, and treatment costs are high.
Bariatric surgery (surgery for weight loss by altering the digestive system) and very low-calorie diets can improve glycemic control and beta-cell function, but less invasive and sustainable solutions are needed. . Further research is essential to identify dietary interventions that restore β-cell function and investigate racial differences in responsiveness.
Participants in this study included African American (AA) and European American (EA) adults with T2D, identified by self-reported race. Inclusion criteria were: diagnosis of T2D within the past 10 years, treatment with dietary changes or specific medications, age between 35 and 65 years, and glycated hemoglobin A1c (HbA1c) ≤8.0. It consisted of having a body mass index (BMI) of 25 to 25. 50. Participants with glucocorticoid use, significant changes in weight, or substance abuse were excluded. Dosing was suspended and fasting blood glucose levels were monitored prior to baseline assessment.
Dietary regimens (CR, HC) were created by a registered dietitian and adjusted weekly, with participants preparing meals at calorie levels aimed at maintaining body weight. At baseline and after 12 weeks, participants underwent a 75 g oral glucose tolerance test (OGTT) and hyperglycemic clamp. Blood samples were collected and analyzed for glucose, insulin, and C-peptide levels. To assess β-cell function, we calculated the first phase C-peptide index and disposition index (DI). Statistical analyzes included analysis of covariance (ANCOVA) and paired t-tests to analyze the influence of diet on outcomes between different ethnic groups.
The study enrolled a total of 65 participants, including AA and EA adults diagnosed with T2D. Eight participants withdrew from the study for various reasons, including personal issues, dietary non-adherence, and closures due to coronavirus disease 2019 (COVID-19). Ultimately, 57 participants completed the 12-week dietary intervention and successfully completed both the baseline OGTT and hyperglycemic clamp, although some participants had data from only one test. provided. First, all participants were removed from any medications they were taking. Three patients restarted metformin during the intervention, two were assigned to the HC diet, and one to the CR diet.
ANCOVA revealed significant results at 12 weeks for acute and maximal C-peptide responses. Overall, the CR diet resulted in a 2-fold increase in acute C-peptide responses compared to the HC diet, and a similar significant improvement was observed in the AA group, but not in the EA group. To maximize C-peptide response, the CR diet showed a 22% increase across participants and a 48% increase in EA specifically. In terms of DI, the CR diet resulted in an overall increase of 32% and AA a significant increase of 48%.
No change in insulin sensitivity was detected from the hyperglycemic clamp, but neither was the Matsuda index derived from the OGTT. Of note, at 12 weeks, β-hydroxybutyric acid (BHB) levels were relatively higher on the CR diet compared to the HC diet, and the increase in BHB was greater in the CR group.
In summary, the results showed that the CR diet significantly enhanced acute and maximal C-peptide responses compared to the HC diet. Although insulin sensitivity was not altered, the CR diet showed potential as a practical approach to restore β-cell function, especially in EA. These findings are consistent with previous studies supporting dietary carbohydrate restriction to improve metabolic health in T2D patients, and the eucaloric CR diet allows for enjoyable eating while enhancing beta-cell function. This suggests that it may be possible to maintain it.