{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,24]],"date-time":"2026-02-24T08:00:08Z","timestamp":1771920008498,"version":"3.50.1"},"reference-count":38,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,2,21]],"date-time":"2026-02-21T00:00:00Z","timestamp":1771632000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Medical University of Bialystok","award":["SUB\/1\/DN\/22\/003\/1150"],"award-info":[{"award-number":["SUB\/1\/DN\/22\/003\/1150"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Residual \u03b2-cell secretory function plays a central role in diabetes pathophysiology; however, long-term comparative data describing \u03b2-cell trajectories from diagnosis across diabetes phenotypes remain limited. In this prospective observational study, 393 adults with newly diagnosed diabetes underwent assessment of fasting and glucagon-stimulated C-peptide at diagnosis. The cohort included individuals with type 1 diabetes mellitus (T1DM), encompassing both classical adult-onset autoimmune diabetes and latent autoimmune diabetes in adults (LADA), as well as individuals with type 2 diabetes mellitus (T2DM). A subgroup of 89 participants underwent follow-up visit after a mean of seven years. Glucagon stimulation testing was not repeated at follow-up in patients with T1DM and LADA for clinical and safety reasons; therefore, longitudinal analyses in these groups are based on fasting C-peptide measurements. At diagnosis, fasting and glucagon-stimulated C-peptide concentrations differed markedly between phenotypes (median fasting C-peptide: 0.87 ng\/mL in T1DM, 1.53 ng\/mL in LADA, and 2.64 ng\/mL in T2DM; stimulated C-peptide: 1.35, 1.86, and 4.60 ng\/mL, respectively; all p &lt; 0.001). During follow-up, patients with T1DM exhibited a pronounced decline in fasting C-peptide (from 0.95 to 0.10 ng\/mL), whereas individuals with T2DM showed preserved or increased stimulated responses (from 4.37 to 5.46 ng\/mL). Participants with LADA displayed intermediate baseline values and a gradual decline in fasting C-peptide (from 1.41 to 0.31 ng\/mL). Higher baseline C-peptide concentrations were associated with more favourable long-term metabolic profiles, including lower insulin resistance and better glycaemic control. These findings demonstrate that the early dynamic assessment of \u03b2-cell reserve using the glucagon stimulation test complements fasting C-peptide by revealing biologically meaningful heterogeneity in disease trajectories, thereby refining phenotypic classification and prognostic stratification at the time of diabetes diagnosis.<\/jats:p>","DOI":"10.3390\/ijms27042035","type":"journal-article","created":{"date-parts":[[2026,2,23]],"date-time":"2026-02-23T08:58:21Z","timestamp":1771837101000},"page":"2035","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Baseline \u03b2-Cell Secretory Reserve and Its Association with Glycaemic Control and Long-Term Outcomes Across Diabetes Phenotypes"],"prefix":"10.3390","volume":"27","author":[{"given":"Rafa\u0142","family":"Maciulewski","sequence":"first","affiliation":[{"name":"Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Bialystok, 15-276 Bialystok, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7403-6928","authenticated-orcid":false,"given":"Angelika","family":"Buczy\u0144ska-Backiel","sequence":"additional","affiliation":[{"name":"Clinical Research Centre, Medical University of Bialystok, 15-276 Bialystok, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anna","family":"Zieli\u0144ska-Maciulewska","sequence":"additional","affiliation":[{"name":"Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Bialystok, 15-276 Bialystok, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Katarzyna","family":"Siewko","sequence":"additional","affiliation":[{"name":"Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Bialystok, 15-276 Bialystok, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4522-4978","authenticated-orcid":false,"given":"Adam","family":"Kr\u0119towski","sequence":"additional","affiliation":[{"name":"Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Bialystok, 15-276 Bialystok, Poland"},{"name":"Clinical Research Centre, Medical University of Bialystok, 15-276 Bialystok, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ma\u0142gorzata","family":"Szelachowska","sequence":"additional","affiliation":[{"name":"Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Bialystok, 15-276 Bialystok, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"American Diabetes Association Professional Practice Committee (2025). 2. 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