Effects of Salmon Nasal Cartilage Proteoglycan on Plasma Glucose Concentration and Active Glucose Transport in the Small Intestine

Abstract

Summary Recently, proteoglycan was purified from the nasal cartilage of salmon. Although several physiological effects have been reported, the effect of salmon nasal cartilage proteoglycan (salmon PG) on glucose metabolism remains unclear. We studied the effect of salmon PG on rat plasma glucose levels. Oral administration of 1% salmon PG significantly attenuated the increase in portal plasma glucose levels following an oral glucose tolerance test (OGTT). Additionally 1% salmon PG delayed the increase in peripheral glucose concentration induced by the OGTT. Mucosal administration of 1% salmon PG significantly decreased active glucose transport using the everted jejunal sac method. Furthermore, transmural potential difference (DPD) measurements using the everted jejunum revealed that 1% salmon PG significantly decreased glucose-dependent and phlorhizin (inhibitor of sodium-glucose co-transporter 1; SGLT1)-sensitive DPD. These results suggest that salmon PG decreases glucose absorption via SGLT1 in the jejunum, thereby attenuating the increase in portal and peripheral plasma glucose levels in rats.

Effects of taurine on plasma glucose concentration and active glucose transport in the small intestine

“…To assess the active glucose transport, the everted sacs (3.0–4.0 cm in length) were prepared from rat jejunums following our previous method (Tsuchiya et al . ). The sacs were filled with Tyrode's solution (119 mmol/L NaCl, 2.4 mmol/L K 2 HPO 4 , 0.6 mmol/L KH 2 PO 4 , 1.2 mmol/L CaCl 2 , 1.2 mmol/L MgCl 2 , 21 mmol/L NaHCO 3 and 10 mmol/L glucose, oxygenated with 95% O 2 /5% CO 2 gas, pH 7.4).…”

“…To measure sodium‐dependent glucose transport, the transmural potential difference (ΔPD) method was followed as described in our previous study (Tsuchiya et al . ). ΔPD was continuously measured by connecting calomel half‐cells to the mucosal and serosal solution by means of a 2% agar bridge, and was recorded using a high‐sensitivity DC chart recorder (056‐1001; HITACHI, Tokyo, Japan) (Hindmarsh et al .…”

The Effects of Dietary Fibers on Improvement of Glucose Metabolism

“…In 2015, Tsuchiya et al [13] found that proteoglycans (PG) are new ingestible polysaccharide-like materials that regulate glucose metabolism [13]. PG is the major non-collagenous extracellular matrix component, particularly in cartilage and skin.…”

“…PG is the major non-collagenous extracellular matrix component, particularly in cartilage and skin. Although it was not food originally, PG was purified abundantly from the nasal cartilage of salmon, not only as a therapeutic agent but also as a food product [13][14][15]. Tsuchiya et al [13] found that oral administration of salmon PG decreased glucose absorption in the jejunum, thereby attenuating the increase in plasma glucose levels in rats.…”

“…Although it was not food originally, PG was purified abundantly from the nasal cartilage of salmon, not only as a therapeutic agent but also as a food product [13][14][15]. Tsuchiya et al [13] found that oral administration of salmon PG decreased glucose absorption in the jejunum, thereby attenuating the increase in plasma glucose levels in rats. As shown in Figure 1, salmon PG belongs to the aggrecan family and is composed of a core protein section attached to glycosaminoglycan (GAG) chains which is the polysaccharide part [16].…”