Use of Continuous Glucose Monitoring to Evaluate Postprandial Response to Raw Cornstarch Supplementation in Adult Glycogen Storage Disease Type I

NCT07645898 | Recruiting

• 1 other identifier: 274-2025
• Study Type: observational
• Target: 8
• Locations: 1 country
• Sites: 1

Brief Summary

The aim of this observational study is to evaluate the impact of raw cornstarch supplementation on postprandial glycemic response in adult patients with Glycogen Storage Disease type I (GSD I), using continuous glucose monitoring (CGM) systems.GSD I is a rare inherited metabolic disorder characterized by impaired glucose homeostasis during fasting, leading to recurrent hypoglycemia and metabolic abnormalities. Nutritional therapy, based on frequent carbohydrate intake and raw cornstarch supplementation, represents the cornerstone of treatment. However, the optimal timing of raw cornstarch administration in relation to meals and its effect on postprandial glycemic control remain unclear.The main question this study aims to answer is: "Does raw cornstarch intake during meals affect postprandial glycemic response in adult patients with Glycogen Storage Disease type I?". Additional objectives include evaluating whether dose and timing of cornstarch intake influences glucose profile, glycemic variability, hypoglycemic events, body composition, energy expenditure, and lipid profile. Participants will include adults with genetically confirmed GSD Ia or Ib who routinely use CGM systems and regularly consume raw cornstarch as part of their dietary management. This is a real-life observational study, and participants will continue their routine clinical care without receiving additional experimental treatments. After providing informed consent, participants will undergo clinical, metabolic, and nutritional assessments, including:

• anthropometric measurements;
• body composition analysis by bioelectrical impedance;
• indirect calorimetry for resting energy expenditure;
• handgrip strength evaluation;
• biochemical analyses, including fasting glucose, HbA1c, lipid profile, liver enzymes, creatinine, uric acid, and lactate. CGM-derived parameters collected during the 14 days preceding the visit will be analyzed, including Time in Range (TIR), Time Above Range (TAR), Time Below Range (TBR), coefficient of variation (CV%), Glucose Management Indicator (GMI), and frequency of hypoglycemic episodes. Participants will also complete a 7-day food diary reporting meal timing, food intake, and raw cornstarch consumption. Investigators will compare meals consumed with and without raw cornstarch supplementation and evaluate postprandial glycemic trends. Postprandial glycemic response will be assessed using dynamic indices, including glucose peak, nadir, time to peak, time to nadir, glucose excursion rates, and incremental area under the curve (iAUC). Glucose values will be analyzed every 5 minutes for up to 4 hours after meals using CGM data. Inclusion criteria include: genetically confirmed GSD Ia or Ib, age \>18 years, routine CGM use, and habitual raw cornstarch consumption.Exclusion criteria include psychiatric disorders, pregnancy, celiac disease, dialysis treatment, nocturnal enteral feeding, and severe acute or chronic illnesses. Approximately 8 adult patients are expected to be enrolled. Risks for participants are considered minimal, as all procedures are part of routine clinical follow-up. Potential benefits include improved personalization of nutritional therapy and optimization of carbohydrate and raw cornstarch administration, potentially improving glycemic control and reducing metabolic complications in patients with GSD I.

Conditions

Glycogen Storage Disease Type I

Keywords

GSD I; Continous Glucose Monitoring; Raw Cornstarch; Glycogen Storage Disease Type I

Outcome Measures

Primary Outcomes (3)

• Incremental Area Under the Glucose Curve (iAUC)

  Incremental area under the postprandial glucose curve (iAUC) following meals with different nutritional composition, with or without raw cornstarch supplementation, assessed using continuous glucose monitoring (CGM). Postprandial glucose excursions will be quantified as incremental area under the glucose curve (iAUC; mg·min/dL) calculated from CGM data collected at 5-minute intervals. iAUC will be calculated from 30 minutes before meal consumption up to 4 hours after the meal

  CGM data will be collected for 14 days from the time of enrollment.

• Postprandial Glucose Excursion Magnitude

  The magnitude of postprandial glucose excursions will be evaluated using CGM-derived glucose concentration parameters, including: Glucose Peak (mg/dL); Glucose Nadir (mg/dL). These measures will be derived from CGM recordings collected at 5-minute intervals during the period extending from 30 minutes before meal consumption to 4 hours after meal consumption.

  CGM data will be collected continuously for 14 days from enrollment.

• Postprandial Glucose Excursion Timing

  The temporal characteristics of postprandial glucose excursions will be evaluated using: * Time to glucose peak (minutes); * Time to glucose nadir (minutes). * Difference between time to peak and time to nadir (minutes) These measures will be derived from CGM recordings collected at 5-minute intervals during the period extending from 30 minutes before meal consumption to 4 hours after meal consumption.

  CGM data will be collected continuously for 14 days from enrollment.

Secondary Outcomes (5)

• Continuous Glucose Monitoring (CGM) Parameters

  CGM data will be collected continuously for 14 days from enrollment and longitudinally across up to four consecutive self-reported menstrual cycles (approximately 16 weeks). Menstrual cycle phase (follicular vs luteal) will be recorded as a time-varying

• Body Composition

  During the follow-up visit, 14 days after the enrollment

• Postprandial Tiglycerides Response

  This assessment will be performed at the second follow-up visit 3 month after enrollment.

• Resting Energy Expenditure

  During the follow-up visit, approximately 14 days after enrollment.

• Substrate Oxidation Percentages

  During the follow-up visit, approximately 14 days after enrollment.

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

Adult patients with genetically confirmed Glycogen Storage Disease type Ia or Ib routinely followed at the Unit of Diabetology of the University Hospital

You may qualify if:

• confirmed genetic diagnosis of GSD Ia or Ib;
• age \>18 years;
• routine CGM use;
• habitual raw cornstarch consumption.

You may not qualify if:

• psychiatric disorders;
• pregnancy, celiac disease;
• dialysis treatment;
• nocturnal enteral feeding;
• severe acute or chronic illnesses.

Sponsors & Collaborators

• Federico II University: lead

Study Sites (1)

AOU Policlinico "Federico II"

Naples, Napoli, 80131, Italy

RECRUITING

Biospecimen

Retention: SAMPLES WITHOUT DNA

Blood samples: one EDTA tube and one serum tube (total blood volume: 5 mL) Urine sample: one 12 mL urine collection tube

MeSH Terms

Conditions

Glycogen Storage Disease Type I

Condition Hierarchy (Ancestors)

Glycogen Storage Disease; Carbohydrate Metabolism, Inborn Errors; Metabolism, Inborn Errors; Genetic Diseases, Inborn; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Metabolic Diseases; Nutritional and Metabolic Diseases

Central Study Contacts

Roberta Lupoli Associated Professor, Medical Director at the AOU Federico II

CONTACT

+39 0817462302; roberta.lupoli@unina.it

Study Design

• Study Type: observational
• Observational Model: CASE ONLY
• Time Perspective: PROSPECTIVE
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Associate Professor, Medical Director

Study Record Dates

• First Submitted: May 12, 2026
• First Posted: June 12, 2026
• Study Start: February 5, 2026
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): February 1, 2027
• Last Updated: June 12, 2026

Record last verified: 2026-06

Data Sharing

• IPD Sharing: Will not share

Locations

IT (1)