Genetics: Is LADA just late onset type 1 diabetes?

Area of Science:

• Immunogenetics
• Endocrinology
• Diabetes Mellitus Classification

Background:

• Ongoing debate exists regarding the classification of Latent Autoimmune Diabetes in Adults (LADA).
• LADA's classification is contested: is it a slow-progressing type 1 diabetes (T1DM) or a distinct entity?
• Understanding LADA's genetic underpinnings is crucial for accurate diagnosis and classification.

Purpose of the Study:

• To investigate the genetic associations of LADA with T1DM and T2DM.
• To compare the prevalence of major T1DM-associated genes (HLA, PTPN22, INS) in LADA patients versus T1DM and T2DM cohorts.
• To clarify LADA's position within the diabetes mellitus spectrum through genetic profiling.

Main Methods:

• Cross-sectional study involving 578 participants: 248 with T1DM, 256 with T2DM, and 74 with LADA.
• Genotyping of class II HLA loci (DRB1, DQA1, DQB1) using reverse PCR sequence-specific oligonucleotides.
• Genotyping of PTPN22 (rs2476601) and INS (rs689) SNPs via real-time PCR.

Main Results:

• High-risk HLA alleles were more frequent in LADA than T2DM; protective alleles showed the opposite trend.
• LADA patients exhibited a lower frequency of a specific high-risk HLA haplotype (DRB1*04-DQB1*03:02-DQA1*03:01) compared to overall T1DM.
• Genetic profiles for PTPN22 and INS SNPs showed differences between LADA and T1DM, but not between LADA and T2DM or LADA and late-onset T1DM.

Conclusions:

• The genetic profile of LADA partially resembles T1DM, particularly T1DM diagnosed later in life, but with fewer risk alleles.
• Significant genetic differences were observed in HLA, PTPN22, and INS genes between LADA and other diabetes types.
• Findings suggest LADA may represent a distinct subtype of diabetes with a unique genetic predisposition.