Browsing by Subject "Insulin resistance"

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Interaction of insulin like growth factor-1 and resistance training on skeletal muscle mass and function
(2002) Lee, Suk-Ho, 1968-; Farrar, Roger P.
In the present study, the effects of IGF-1 overexpression, resistance training and their interaction on muscle mass and function were examined in both mouse and rat models. In addition, the effect of IGF-1 overexpression on the reversal of training-induced adaptations in skeletal muscle mass and function during varying lengths of detraining was measured. The resistance training consisted of a ladder climbing protocol. Overexpression of IGF-1 was localized to one hindlimb via injections containing adeno-associated virus and the contralateral hindlimb served as an internal control. IGF-1 overexpression alone resulted in an increase in mass and peak tetanic tension (Po) of the flexor hallucis longus (FHL) muscle in both rat and mouse model. Eight weeks of resistance training alone resulted in an increase in mass and peak tetanic tension (Po) of the flexor hallucis longus (FHL) muscle only in rat model. The combination of resistance training and IGF-1 overexpression resulted in further increase in muscle mass and Po in rat model, giving evidence of an additive effect. Overexpression of IGF-1 significantly attenuated the loss of muscle mass in FHL during 12 weeks of detraining. These data suggest a beneficial effect of combination of resistance training and IGF-1 overexpression on skeletal muscle mass and function.
Metabolic syndrome and insulin resistance in overweight/obese women in early postpartum
(2009-12) Lu, Hongxing; Freeland-Graves, Jeanne H.; Jolly, Christopher A.; Ciolino, Henry P.; Lewis, Karron G.; Xu, Bugao
Metabolic syndrome includes several metabolic and hormonal disorders, such as abdominal obesity, insulin resistance, and lower blood ghrelin. Women with breastfeeding history exhibit a reduced risk for metabolic syndrome in later life. The purpose of aim 1 was to determine the incidence of metabolic syndrome in low income, overweight/obese women in early postpartum and to assess its relationship to lactation status. It has been found that the incidence of metabolic syndrome is much higher in formula feeding women than that of the breastfeeding ones (44.3% vs. 22.4%, p < 0.01). The breastfeeding mothers had reduced triglycerides (109.07 mg/dl vs. 143.10 mg/dl, p < 001) and elevated serum high-density lipoprotein (HDL)-cholesterol (58.59 mg/dl vs. 51.76 mg/dl, p < 0.01). The goal of aim 2 was to explore associations between ghrelin, metabolic syndrome and infant feeding methods in low income, overweight/obese women in early postpartum. In our study, the breastfeeding mothers in early postpartum had higher plasma ghrelin, as compared to those who formula fed (584.73 pg/ml vs. 450.77 pg/ml, p < 0.01). Additionally, it is found that plasma ghrelin was negatively associated with incidence and numbers of risk factors for metabolic syndrome, before and after controlling for body mass index (BMI). After adjusting for ghrelin in logistic regression analyses, significant relationships between lactation status and metabolic syndrome disappeared. Thus, the protective function of breastfeeding against metabolic syndrome in overweight/obese women in early postpartum may related to the plasma ghrelin values. The purpose of aim 3 was to detect the influence of weight loss on insulin resistance and plasma adiponectin, zinc (Zn), manganese (Mn) and copper (Cu) in low income, overweight/obese women in early postpartum. After an eight-week weight loss intervention, plasma levels of adiponectin, Zn and Mn were significantly enhanced, and plasma concentrations of insulin (7.53±0.56 vs. 6.23±0.49, p <0.01) and insulin resistance (1.84±0.15 vs. 1.44±0.12, p <0.01) were reduced. The increase of adiponectin, Zn and Mn was positively associated with weight reduction. However, the plasma Cu was not significantly affected. The relationships between weight loss and reduced insulin resistance disappeared after adjusting the increases of adiponectin, Zn and Mn during weight loss. Thus, weight loss had beneficial effects on insulin resistance, plasma values of adiponectin Zn and Mn. It is plausible that the influence of weight loss on insulin resistance may be associated with improvements of plasma of adiponectin, Zn and Mn. Collectively, the results of this study demonstrate the important benefits of breastfeeding on prevention of metabolic syndrome in overweight/obese women in early postpartum. This study also emphasizes the influence of ghrelin on risk factors of metabolic syndrome and lactation status.
Regulation of the expression of adiponectin, resistin, and GLUT4 in omental adipose tissue of baboon
(2003) Tejero-Barrera, Maria Elizabeth; Freeland-Graves, Jeanne H.
The purpose of this research was to identify the chromosomal regions influencing the mRNA expression of the hormones resistin and adiponectin, and the glucose transporter 4 (GLUT4) in omental adipose tissue of baboons. These baboon genes were cloned using a two-step reverse transcription- polymerase chain reaction (RT-PCR) technique. Real- time, quantitative RT-PCR assays were developed and standardized for measurement of mRNA levels of each gene. Total RNA was isolated from 460 samples of adipose tissue from adult pedigreed baboons, and used for the quantification of adiponectin, resistin and GLUT4 mRNA. Quantitative genetic analyses were conducted using the mRNA abundance of each gene as a quantitative phenotype applying the variance decomposition approach. Heritabilities were calculated for resistin (h2 = 0.23, p = 0.005), adiponectin (h2 = 0.23, p = 0.001) and GLUT4 (h2 = 0.24, p = 0.001). Genome scan analyses were conducted to locate the chromosomal regions influencing the expression of the studied genes. The identified regions and corresponding LOD scores are: 19p13 (LOD score = 3.8) for resistin, 6q13 (LOD score =1.6) for adiponectin mRNA and same location (LOD score =1.0) for adiponectin protein, and 10q24-26 (LOD score = 1.4) for GLUT4 mRNA. A parallel study in 120 baboons indicated a relationship between body weight and indicators for insulin sensitivity, and an association between adiponectin levels and insulin resistance (HOMA-IR index) in baboons. No correlation between the analyzed phenotypes and resistin expression in monocytes was found. The relationships between mRNA expression in adipose tissue of resistin, adiponectin and GLUT4 and circulating levels of selected cytokines (TNFa, IL-6 and IL-1b) and phenotypes associated to insulin resistance were investigated in a sub-sample of unrelated baboons (n=40). Resistin expression in adipose tissue was related to insulin sensitivity, adiponectin mRNA was inversely associated with cytokines in plasma, and GLUT4 abundance and the HOMA-IR index were correlated. Collectively, these results revealed novel findings on the genetic component of the endocrine function of adipose tissue, and confirmed the value of the baboon as a model for the genetic study of obesity-related conditions.