Curious Now

Story

Detection of pancreatic beta cell mass in vivo in humans: studies in individuals with long-standing type 1 diabetes and in individuals with obesity

Life SciencesHealth & Medicine

Key takeaway

Researchers developed a new imaging technique that can measure pancreatic beta cell mass in living humans, which could help diagnose and monitor diabetes.

Read the paper

Quick Explainer

This study used PET-CT imaging with a radioactive exendin-4 tracer to measure pancreatic beta cell mass (BCM) in people with long-standing type 1 diabetes and obesity. The tracer binds to beta cell receptors, allowing the researchers to quantify BCM based on the PET-CT signal. They found that BCM was significantly lower in the type 1 diabetes group compared to the obesity group. Importantly, in the obesity group, the BCM measurements correlated with a biomarker of beta cell function, suggesting the PET-CT approach can provide valuable insights into the relationship between beta cell mass and function. These non-invasive BCM biomarkers have potential clinical utility for monitoring beta cell health in diabetes and metabolic conditions.

Deep Dive

Technical Deep Dive: Detection of pancreatic beta cell mass in vivo in humans

Overview

This study aimed to assess biomarkers of pancreatic beta cell mass (BCM) derived from 68Ga-NODAGA-exendin-4 PET-CT scans in individuals with long-standing type 1 diabetes (T1DM) and in individuals with obesity (OBESE). It also investigated the relationship between these BCM biomarkers and a biomarker of beta cell functional mass (BCFxM) in the OBESE group.

Methodology

  • 8 participants with T1DM (age 50.4±3.8 years, T1DM duration 34.2±3.0 years, BMI 26.6±1.1 kg/m^2, HbA1c 7.5±0.36%) and 9 participants with OBESE (age 48.2±2.2 years, BMI 37.4±1.1 kg/m^2, HbA1c 5.4±0.17%) underwent two study procedures:
    1. 68Ga-NODAGA-exendin-4 PET-CT scans of the pancreas (PX) and parotid glands 45-60 minutes after IV injection, with CT assessment of PX volume to compute BCM biomarkers:
      • BCMSUV: based on standardized uptake values (SUV)
      • BCMCLEAR: based on exendin-4 clearance (CLEAR)
    2. Mixed meal tests (MMT) with measurement of plasma glucose, C-peptide, GLP-1 and GIP to assess BCFxM using mathematical modeling.

Results

  • The C-peptide response to the MMT was absent or negligible in T1DM, but robust in OBESE, indicating reduced BCFxM in T1DM.
  • The PX volume was 51.7±6.6 cc in T1DM, significantly smaller than 92.9±10.9 cc in OBESE (p=0.007).
  • The BCM biomarkers BCMSUV and BCMCLEAR were 6.6-fold (p=0.003) and 5.0-fold (p=0.002) lower, respectively, in T1DM compared to OBESE.
  • In OBESE, the BCFxM was positively correlated with both BCMSUV (r=0.91, p<0.001) and BCMCLEAR (r=0.82, p=0.006).

Interpretation

  • The 68Ga-NODAGA-exendin-4 derived biomarkers of BCM can effectively discriminate T1DM from OBESE individuals.
  • In OBESE, the 68Ga-NODAGA-exendin-4 derived BCM appears to be a key determinant of the beta cell response to the MMT.
  • These BCM biomarkers may be valuable to compare and monitor BCM in both research and clinical settings.

Limitations & Uncertainties

  • The study had a relatively small sample size (8 T1DM, 9 OBESE).
  • It is unclear if the BCM biomarkers can detect more subtle changes in BCM, such as in early stage type 2 diabetes.
  • The relationship between the BCM biomarkers and actual beta cell mass is not conclusively established.

What Comes Next

  • Larger studies are needed to further validate the BCM biomarkers and their clinical utility.
  • Investigating the BCM biomarkers in earlier stages of diabetes and other metabolic conditions could provide additional insights.
  • Improving the specificity of the exendin-4 tracer for beta cells versus exocrine pancreas may enhance the BCM biomarkers.

Source