ORIGINAL ARTICLE Yacon supplementation reduces serum free fatty acids and tumor necrosis factor alpha concentrations in patients with type 2 diabetes Hiroaki Satoh • Akihiro Kudoh • Koji Hasegawa • Hiroyuki Hirai • Tsuyoshi Watanabe Received: 28 May 2013 / Accepted: 28 October 2013 Ó The Japan Diabetes Society 2013 Abstract Yacon is a perennial plant originating from South America that forms [ 20 large subterranean tubers weighing from 100 to 500 g. These tubers have become popular in Japan and contain beta-1, 2-oligofructans as the main saccharides. Preliminary work in animals revealed yacon feeding ameliorates diabetes by reducing blood glucose. We therefore examined whether yacon feeding modulates glucose metabolism in patients with type 2 diabetes. We conducted a single-center, open-label, ran- domized controlled trial to investigate the effect of yacon on patients with type 2 diabetes. Fifty-eight patients with type 2 diabetes were selected from the medical outpatients department. There had been no changes in their diet or medications during the 3 months before the study com- menced. After ethical clearance, written informed consent was obtained. Patients were randomly assigned to two groups: group 1 received an intake level of 100 g yacon/ day, and group 2 received an intake level of 100 g aroid/ day (control). Fasting glucose, insulin, glycated albumin, and adiponectin concentrations at baseline did not differ significantly between groups; after 5 months, concentra- tions did not change significantly in either group. Inter- estingly, after 5 months of yacon consumption, tumor necrosis factor alpha (TNF-a) and free fatty acid (FFA) concentrations decreased significantly by 10.3 % and 9.8 % (p \ 0.01), respectively; neither changed signifi- cantly in the aroid group. In conclusion, the results suggest longer-term yacon supplementation may improve insulin resistance by reducing FFA and TNF-a in patients with type 2 diabetes. Keywords Yacon Á TNF-a Á Free fatty acids Á Type 2 diabetes Abbreviations TNF-a Tumor necrosis factor alpha FFAs Free fatty acids LMW Low molecular weight MMW Middle molecular weight HMW High molecular weight FOS b-1, 2-fructooligosaccharides RLP-C Remnant-like particle cholesterol IRS-1 Insulin receptor substrate 1 Introduction Insulin resistance and obesity are key features of metabolic syndrome and type 2 diabetes [1]. One potential mecha- nism involves the production of hormones, or adipocyto- kines, by adipose tissue. Plasma concentrations of many adipocytokines, such as leptin, tumor necrosis factor alpha (TNF-a), free fatty acids (FFAs), and resistin, are posi- tively associated with insulin resistance, whereas adipo- nectin is negatively associated with insulin resistance [2, 3]. In addition, circulating adiponectin exists predomi- nantly as low molecular weight (LMW) trimers, middle molecular weight (MMW) hexamers, and high molecular weight (HMW) complexes believed to possess different biological activities [4]. HMW adiponectin is believed to be more closely associated with insulin sensitivity and considered to be a relatively more metabolically active H. Satoh (&) Á A. Kudoh Á K. Hasegawa Á H. Hirai Á T. Watanabe Department of Nephrology, Hypertension, Diabetology, Endocrinology, and Metabolism, Fukushima Medical University, 1 Hikarigaoka, Fukushima City, Fukushima 960-1295, Japan e-mail: hiroakis-tky@umin.ac.jp 123 Diabetol Int DOI 10.1007/s13340-013-0150-y