Increased Frequency of β Cells with Abnormal NKX6.1 Expression in Type 2 Diabetes but not in Subjects with Higher Risk for Type 2 Diabetes

Abstract

Background: NKX6.1 is a transcription factor for insulin, as well as a marker for β cell maturity. Abnormal NKX6.1 expression in β cells, such as translocation from the nucleus to cytoplasm or lost expression, has been shown as a marker for β cell dedifferentiation.Methods: Here, we obtained pancreata sections from organ donors, and aim to characterize NKX6.1 expression in subjects with or without type 2 diabetes mellitus (T2DM), and NKX6.1 and insulin immunofluorescence staining was performed.Results: Our results showed that cells with insulin expression but no nucleic NKX6.1 expression (NKX6.1 Nuc- Ins + ), and cells with cytoplasmic NKX6.1 expression but no insulin expression (NKX6.1 cyt Ins - ) were significantly increased in T2DM subjects and positively correlated with glycated hemoglobin (HbA1c), indicating the elevated β cell dedifferentiation with NKX6.1 inactivation in T2DM. To investigate whether β cell dedifferentiation has initiated in subjects with higher risks for T2DM, we next analyzed the association between β-cell dedifferentiation level in ND subjects with different ages, body mass index, and HbA1c. The results showed the absolute number and percentage of dedifferentiated β cells with NKX6.1 inactivation did not significantly change in subjects with advanced aging, obesity, or modest hyperglycemia, indicating that the β cell dedifferentiation may mainly occur after T2DM was diagnosed.Conclusion: In sum, our results suggested that NKX6.1 expression in β cells is changed in type 2 diabetic subjects, evidenced by significantly increased NKX6.1 Nuc- Ins + and NKX6.1 cyt Ins - cells. This abnormality does not occur more frequently in subjects with a higher risk for T2DM, suggesting that β cell dedifferentiation might be secondary to the pathological changes in T2DM.

Deficiency of transcription factor Nkx6.1 does not prevent insulin secretion in INS-1E cells

“…For example, insulin-glucagon bihormonal cells exist as a 3 to 4% fraction in islets of type 2 diabetic subjects, elevated up to 16% by incretin treatment 47 . Also, an abnormal Nkx6.1 expression was found in type 2 diabetic subjects 48 . Moreover, there is a phenomenon of β-cell degranulation exists, referring to the depletion of insulin granules initiated by a metabolic stress with an unchanged transcriptome (at least transiently upon a retarded response) 44 .…”

Identification of two β-cell subtypes by 7 independent criteria

“…These challenges stem partly from technological inadequacies of scRNA-seq itself, and from rational use of genetic tools such as transgenic reporters that are by definition artificial, generate heterogeneity themselves and may not express reproducibly in all cells of a given compartment (e.g. widely used Nkx6.1 reporter lines while highly valuable express in ~80% of β-cells (Liu et al, 2021)). We focused our approach on evaluating heterogeneity across all β-cells.…”