Lactate is an important metabolite in cellular metabolism and fluctuates in certain disease conditions including cancer and immune diseases. It was hypothesized that a decrease in lactate would modulate the inflammatory response elicited by lipopolysaccharides (LPS) in macrophages. When RAW 264.7 macrophages were treated with FX11, a specific lactate dehydrogenase (LDHA) inhibitor, the expression of the cytokines, inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX‑2) was downregulated due to reduced cellular lactate levels. Genetic suppression of LDHA by small interfering RNA (siRNA) downregulated the LPS‑activated expression of interleukin (IL)‑6, iNOS, and COX‑2, and reduced the production of IL‑6 and nitrites. Pharmacological and genetic suppression of LDHA inhibited the phosphorylation of p38 mitogen‑activated protein kinase. Microarray gene expression profile demonstrated that the genes involved in cell proliferation and inflammation were mainly altered by siRNA‑mediated LDHA suppression. Collectively, the present observations suggest that lactate may be an important metabolite and implicated in regulation of inflammatory response.

Green tea is being studied extensively for its postprandial hypoglycemic effect due to its abundant catechins. Along with catechins, water-soluble green tea polysaccharides are also currently gaining attention due to their natural hypoglycemic properties. The current study investigated the combinational effect of green tea extract (GTE) and crude green tea polysaccharides (CTP) in inhibiting glucose transport after digestion of rice starch, using an in vitro digestion model with a Caco-2 cell. Co-digestion of rice starch with GTE (16.09 ± 1.02 g L⁻¹), CTP (16.83 ± 0.81 g L⁻¹), or GTE + CTP (17.79 ± 0.80 g L⁻¹) hydrolyzed less starch into glucose compared with the control (18.24 ± 0.45 g L⁻¹). Glucose transport from digesta to the Caco-2 cell after 120 min incubation was significantly inhibited with GTE + CTP (53.26 ± 4.34%). Gene expression of intestinal glucose transporters, which included sodium-dependent glucose transporter (SGLT1) and glucose transporter 2 (GLUT2), was not altered by GTE, CTP or GTE + CTP, except for the GTE-mediated upregulation of GLUT2. It is concluded that GTE + CTP lowered digestibility of rice starch with glucose and also delayed glucose uptake to the intestinal epithelium. This finding suggests a potential for green tea polysaccharides as a natural postprandial hypoglycemic substance.

Suwon Jeon, Jaehwi Song, Dongyup Lee, Goon-Tae Kim, Si-Hyun Park, Dong-Yoon Shin, Kyong-Oh Shin, Kyungho Park, Soon-Mi Shim, Tae-Sik Park