A low-glycemic index diet and exercise intervention reduces TNF(alpha) in isolated mononuclear cells of older, obese adults

Abstract

Low-glycemic index diets and exercise independently improve glucose tolerance and reduce diabetes risk. However, the combined effect of a low-glycemic index diet and exercise on inflammation and glucose metabolism is not known. Therefore, we randomized 28 insulin-resistant adults (age: 66 ± 1 y; BMI: 34.2 ± 0.7 kg · m(-2)) to a 12-wk, low (LGI = 40) or high- (HGI = 80) glycemic index diet plus aerobic exercise (5 d · wk(-1), 60 min · d(-1), 80-85% heart rate(max)) intervention. All food and fluids were provided during the study. Inflammation was assessed from cytokine (TNFα and IL-6) secretion using peripheral blood mononuclear cells (MNC) stimulated overnight with LPS. Glycemic response was determined following ingestion of a 75-g glucose solution. Fasting blood samples were collected for additional cytokine [TNFα, IL-6, and monocyte chemoattractant protein 1 (MCP-1)] analysis. Both interventions decreased BMI (P < 0.001), fasting plasma glucose (P = 0.01), and insulin (P = 0.02). The glycemic response was reduced only in the LGI group (P = 0.04). Plasma and MNC-derived TNFα secretion were reduced in the LGI group (P = 0.02) but increased in the HGI group (P = 0.02). Secretion of IL-6 from MNC and plasma IL-6 and MCP-1 concentrations were reduced in the LGI group. The change in MNC-derived TNFα (r = 0.43; P = 0.04) and plasma MCP-1 (r = 0.44; P = 0.04) correlated with decreases in the glycemic response. These data highlight the importance of diet composition in the treatment and prevention of inflammation and hyperglycemia. A low-glycemic index diet has antiinflammatory and antidiabetogenic effects when combined with exercise in older, obese prediabetics.

Conflict of interest statement

Author disclosures: K. R. Kelly, J. M. Haus, T. P. J. Solomon, A. J. Patrick-Melin, M. Cook, M. Rocco, H. Barkoukis, and J. P. Kirwan, no conflicts of interest.

Figures

FIGURE 1

Changes in MNC (A,C) and plasma (B,D) TNFα (A,B) and IL-6 (C,D) in older, obese adults who consumed a LGI or HGI diet for 12 wk. Data are means ± SEM for the change in pre- to postintervention values, LGI (n = 13), HGI (n = 15). #Change pre- to postintervention, P < 0.05; *LGI and HGI differ, P < 0.05.

FIGURE 2

Correlations between the change in glycemic response and the changes in TNFα secretion from MNC (A) and plasma MCP-1 concentrations (B) in older, obese adults who consumed a LGI or HGI diet for 12 wk. Data are pre- minus postintervention values, n = 28.