Structural determinants of beta-cell failure in type 2 diabetes: a multimodality imaging study

BACKGROUND: Individuals with type 2 diabetes (T2D) tend to have a smaller pancreas and lower beta-cell mass; however, whether this is cause or consequence of T2D is unclear. We investigated the connection between pancreatic volume, beta-cell mass, beta-cell function, and T2D risk, and whether intrapancreatic fat deposition (IPFD) modifies these associations. METHODS: Ga]Ga-NODAGA-exendin-4 PET/CT imaging, and its correlations with CT-measured pancreatic volume, IPFD, and beta-cell function (HOMA2-%B) were evaluated. In a cross-sectional study using UK Biobank (N = 25,212), individuals were classified into four groups according to median pancreatic volume and IPFD on MRI, and the association with T2D prevalence was estimated. Finally, a case-cohort study with 6-year follow-up (N = 2168, subcohort of 658 and 146 incident T2D cases) used CT imaging to assess whether pancreatic volume and IPFD were associated with future T2D. RESULTS: In the PET/CT study, smaller pancreatic volume (r = 0.66 [95% CI: 0.47-0.80]) combined with higher IPFD (r = 0.29 [95% CI: 0.011-0.53]) was associated with reduced estimated beta-cell mass, which in turn was linked to lower insulin secretion (r = 0.48 [95% CI: 0.22-0.68]). In the UK Biobank, individuals with small pancreas that contained much fat (small/high-fat pancreas) had the highest T2D likelihood (adjusted-odds ratio: 1.71 [95% CI: 1.42-2.07]) compared to those with large/low-fat pancreas. Validation in the longitudinal study showed adjusted-hazard ratios for T2D of 3.12 (1.40-6.96) for small/high-fat, 0.99 (0.58-1.67) for large/high-fat, and 0.74 (0.26-2.14) for small/low-fat pancreas. CONCLUSION: The combination of a small pancreas and high IPFD is associated with increased T2D risk, supporting a structural phenotype linked to beta-cell failure.