Higher Serum Ferritin in Tibetan and Han Populations with Diabetes Living on the Tibetan Plateau

Objective: Tissue iron has emerged as a significant risk factor for diabetes. Pathways that sense and regulate iron and oxygen interact, but few studies examined the interactions of hypoxia and iron in determining diabetes risk in human populations. Accordingly, metabolic phenotyping with analysis of iron homeostasis in both Tibetan and Han Chinese living at 2300-3900m altitudes were conducted. Research design and methods: Data were collected on Tibetan and Han Chinese living at intermediate altitudes. Iron homeostatic and metabolic parameters including homeostasis model assessments (HOMA), hemoglobin A1c, serum ferritin and transferrin saturation were determined. Results: Serum ferritin is higher in both Tibetan groups compared to the respective Han groups, and higher in each diabetic group compared to nondiabetics of the same ethnicity. Serum iron and transferrin saturation were also higher in the Tibetan diabetics than the Tibetan non-diabetics. Serum iron was significantly correlated with ferritin levels in the four combined groups (r2=0.07313, p<0.05) and even stronger in the Tibetan diabetic group (r2=0.2702, p<0.05). HOMA-β was negatively correlated with ferritin in the Tibetan combined groups (r2=0.020, p<0.05), and HOMA-IR tended to be positively correlated with ferritin (r2=0.018, p<0.05). Conclusion: Iron parameters differ both between Han and Tibetans and between diabetics and nondiabetics of both populations. High ferritin, which in these cohorts reflects iron status, is a risk factor for diabetes in both groups, although how iron status relates to the diabetes phenotype differs between the two groups, possibly related to their differing histories of adaptation to high altitude.