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Keywords:

  • beta cell function;
  • glycated haemoglobin;
  • high-sensitivity C-reactive protein;
  • insulin sensitivity;
  • lipid profile;
  • oral glucose tolerance test

Aim:  The extract of the white-skinned sweet potato Ipomoea batatas (Caiapo) has been shown to ameliorate glucose control by improving insulin sensitivity in patients with type 2 diabetes mellitus (T2DM). The present study was designed to further evaluate its mode of action on insulin sensitivity over an extended period of time as well as the effects on fibrinogen and other markers of low-grade inflammation.

Methods:  In this randomized trial, 27 patients with T2DM on diet only received 4 g of Caiapo daily for 5 months; 34 patients placebo. Before and after therapy, insulin sensitivity [oral glucose insulin sensitivity (OGIS), as glucose clearance from oral glucose tolerance test], parameters of diabetes control, lipids, plasma adiponectin, high-sensitivity C-reactive protein (hs-CRP) and fibrinogen were measured.

Results:  Following Caiapo, we observed an increase in OGIS (293 ± 15 vs. 321 ± 12 ml/m2/min, p = 0.0072) and adiponectin (5.97 ± 0.65 to 6.63 ± 0.70 μg/ml, p = 0.013), while fibrinogen decreased from 3.83 ± 0.16 to 3.64 ± 0.18 mg/ml (p = 0.02). This was associated with an improvement in glycated haemoglobin (HbA1c: 6.46 ± 0.12 vs. 6.25 ± 0.11%, p = 0.008), fasting glucose (138 ± 4 vs. 128 ± 5 mg/dl, p = 0.039) and triglycerides (2.36 ± 0.22 vs. 2.07 ± 0.25 mmol/l, p = 0.032). Body weight, lipid levels and hs-CRP were not altered. No changes were observed in the placebo group except for HbA1c, which significantly increased from 6.25 ± 0.10 to 6.50 ± 0.12% (p = 0.0001).

Conclusions:  This study confirms the beneficial effects of Caiapo on glucose and HbA1c control in patients with T2DM after 5 months follow-up. Improvement of insulin sensitivity was accompanied by increased levels of adiponectin and a decrease in fibrinogen. Thus, Caiapo can be considered as natural insulin sensitizer with potential antiatherogenic properties.