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1.  Differences in the GH-IGF-I axis in children of different weight and fitness status 
To determine if differences in the GH-IGF-I axis exist between children of high and low aerobic fitness who are obese or of normal weight.
124 children (ages 8–11) divided into four groups based on BMI and VO2max (mL O2/kg fat free mass(FFM)/min): normal weight — high-fit (NH), normal weight — low-fit (NL), obese — high-fit (OH), and obese — low-fit (OL). Height, weight, skinfolds, body mass index (BMI), body fat percentage and predicted VO2max (both ml/kg/min and ml/kgFFM/min) were assessed. Resting growth hormone (GH), total insulin-like growth factor 1 (total IGF-I), free insulin-like growth factor 1(free IGF-I), and insulin were measured using morning fasting blood samples.
GH was greater in the NH group compared to the OL group only (p<0.01). No group differences existed for either total IGF-I (p=0.53) or free IGF-I (p=0.189). Insulin was greater in the OH and OL groups than the NH and NL groups (p<0.01). With groups combined (or overall), insulin and free IGF-I were related to fitness (insulin — ml/kg/min: r=−0.226, p<0.05 and ml/kgFFM/min: r= −0.212, p < 0.05; free IGF-I — ml/kg/min: r=−0.219, p<0.01 and ml/kgFFM/min: r= −0.272, p < 0.05).
Fitness may contribute to the obesity related reduction of GH that may be involved with weight gain.
PMCID: PMC3566556  PMID: 22436514
Insulin; Fat free mass; VO2max; Aerobic fitness; Youth
2.  Population-specific coding variant underlies genome-wide association with adiponectin level 
Human Molecular Genetics  2011;21(2):463-471.
Adiponectin is a protein hormone that can affect major metabolic processes including glucose regulation and fat metabolism. Our previous genome-wide association (GWA) study of circulating plasma adiponectin levels in Filipino women from the Cebu Longitudinal Health and Nutrition Survey (CLHNS) detected a 100 kb two-SNP haplotype at KNG1–ADIPOQ associated with reduced adiponectin (frequency = 0.050, P = 1.8 × 10−25). Subsequent genotyping of CLHNS young adult offspring detected an uncommon variant [minor allele frequency (MAF) = 0.025] located ∼800 kb from ADIPOQ that showed strong association with lower adiponectin levels (P = 2.7 × 10−15, n = 1695) and tagged a subset of KNG1–ADIPOQ haplotype carriers with even lower adiponectin levels. Sequencing of the ADIPOQ-coding region detected variant R221S (MAF = 0.015, P = 2.9 × 10−69), which explained 17.1% of the variance in adiponectin levels and largely accounted for the initial GWA signal in Filipinos. R221S was not present in 12 514 Europeans with previously sequenced exons. To explore the mechanism of this substitution, we re-measured adiponectin level in 20 R221S offspring carriers and 20 non-carriers using two alternative antibodies and determined that the presence of R221S resulted in artificially low quantification of adiponectin level using the original immunoassay. These data provide an example of an uncommon variant responsible for a GWA signal and demonstrate that genetic associations with phenotypes measured by antibody-based quantification methods can be affected by uncommon coding SNPs residing in the antibody target region.
PMCID: PMC3276282  PMID: 22010046
3.  Adiponectin Decreases Pulmonary Arterial Remodeling in Murine Models of Pulmonary Hypertension 
Remodeling of the pulmonary arteries is a common feature among the heterogeneous disorders that cause pulmonary hypertension. In these disorders, the remodeled pulmonary arteries often demonstrate inflammation and an accumulation of pulmonary artery smooth muscle cells (PASMCs) within the vessels. Adipose tissue secretes multiple bioactive mediators (adipokines) that can influence both inflammation and remodeling, suggesting that adipokines may contribute to the development of pulmonary hypertension. We recently reported on a model of pulmonary hypertension induced by vascular inflammation, in which a deficiency of the adipokine adiponectin (APN) was associated with the extensive proliferation of PASMCs and increased pulmonary artery pressures. Based on these data, we hypothesize that APN can suppress pulmonary hypertension by directly inhibiting the proliferation of PASMCs. Here, we tested the effects of APN overexpression on pulmonary arterial remodeling by using APN-overexpressing mice in a model of pulmonary hypertension induced by inflammation. Consistent with our hypothesis, mice that overexpressed APN manfiested reduced pulmonary hypertension and remodeling compared with wild-type mice, despite developing similar levels of pulmonary vascular inflammation in the model. The overexpression of APN was also protective in a hypoxic model of pulmonary hypertension. Furthermore, APN suppressed the proliferation of PASMCs, and reduced the activity of the serum response factor–serum response element pathway, which is a critical signaling pathway for smooth muscle cell proliferation. Overall, these data suggest that APN can regulate pulmonary hypertension and pulmonary arterial remodeling through its direct effects on PASMCs. Hence, the activation of APN-like activity in the pulmonary vasculature may be beneficial in pulmonary hypertension.
PMCID: PMC3175561  PMID: 21075862
pulmonary hypertension; pulmonary artery smooth muscle cells; metabolism; adiponectin
4.  Mice deficient in mitochondrial glycerol-3-phosphate acyltransferase-1 have diminished myocardial triacylglycerol accumulation during lipogenic diet and altered phospholipid fatty acid composition 
Biochimica et Biophysica Acta  2008;1781(6-7):352-358.
Glycerol-3-phosphate acyltransferase-1 (GPAT1), which is located on the outer mitochondrial membrane comprises up to 30% of total GPAT activity in the heart. It is one of at least four mammalian GPAT isoforms known to catalyze the initial, committed, and rate limiting step of glycerolipid synthesis. Because excess triacylglycerol (TAG) accumulates in cardiomyocytes in obesity and type 2 diabetes, we determined whether lack of GPAT1 would alter the synthesis of heart TAG and phospholipids after a 2-week high sucrose diet or a 3-month high fat diet. Even in the absence of hypertriglyceridemia, TAG increased 2-fold with both diets in hearts from wildtype mice. In contrast, hearts from Gpat1−/− mice contained 20–80% less TAG than the wildtype controls. In addition, hearts from Gpat1−/− mice fed the high-sucrose diet incorporate 60% less [14C]palmitate into heart TAG as compared to wildtype mice. Because GPAT1 prefers 16:0-CoA to other long chain acyl-CoA substrates, we determined the fatty acid composition of heart phospholipids. Compared to wildtype littermate controls, hearts from Gpat1−/− mice contained a lower amount of 16:0 in phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine/phosphatidylinositol and significantly more C20:4n6. Phosphatidylcholine and phosphatidylethanolamine from Gpat1−/− hearts also contained higher amounts of 18:0 and 18:1. Although at least three other GPAT isoforms are expressed in the heart, our data suggest that GPAT1 contributes significantly to cardiomyocyte TAG synthesis during lipogenic or high fat diets and influences the incorporation of 20:4n6 into heart phospholipids.
PMCID: PMC3285559  PMID: 18522808
obesity; type 2 diabetes; lipotoxicity; diabetic cardiomyopathy; arachidonic acid
Hepatology (Baltimore, Md.)  2009;50(2):592-600.
Acute exposure to lipopolysaccharide (LPS) can cause hypoglycemia and insulin resistance; the underlying mechanisms however, are unclear. We set out to determine whether insulin resistance is linked to hypoglycemia through TLR4, MyD88 and NFκB, a cell signaling pathway that mediates LPS induction of the proinflammatory cytokine TNFα. LPS induction of hypoglycemia was blocked in TLR4−/− and MyD88−/− mice but not in TNFα−/− mice. Both glucose production and glucose utilization were decreased during hypoglycemia. Hypoglycemia was associated with the activation of NFκB in the liver. LPS inhibition of glucose production was blocked in hepatocytes isolated from TLR4−/− and MyD88−/− mice and hepatoma cells expressing an IκB mutant that interferes with NFκB activation. Thus, LPS-induced hypoglycemia was mediated by the inhibition of glucose production from the liver through the TLR4, MyD88, NFκB pathway, independent of LPS induced TNFα. LPS inhibition of glucose production was not blocked by pharmacologic inhibition of the insulin signaling intermediate PI3K in hepatoma cells. Insulin injection caused a similar reduction of circulating glucose in TLR4−/− and TLR4+/+ mice. These two results suggest that LPS and insulin inhibit glucose production by separate pathways. Recovery from LPS induced hypoglycemia was linked to glucose intolerance and hyperinsulinemia in TLR4+/+ mice, but not in TLR4−/− mice.
Insulin resistance is linked to the inhibition of glucose production by the TLR4, MyD88 and NFκB pathway.
PMCID: PMC2822400  PMID: 19492426
6.  Neuroendocrine inhibition of glucose production and resistance to cancer in dwarf mice 
Experimental gerontology  2008;44(1-2):26-33.
Pit1 null (Snell dwarf) and Proph1 null (Ames dwarf) mutant mice lack GH, PRL and TSH. Snell and Ames dwarf mice also exhibit reduced IGF-I, resistance to cancer and a longer lifespan than control mice. Endogenous glucose production during fasting is reduced in Snell dwarf mice compared to fasting control mice. In view of cancer cell dependence on glucose for energy, low endogenous glucose production may provide Snell dwarf mice with resistance to cancer. We investigated whether endogenous glucose production is lower in Snell dwarf mice during feeding. Inhibition of endogenous glucose production by glucose injection was enhanced in 12 to 14 month-old female Snell dwarf mice. Thus, we hypothesize that lower endogenous glucose production during feeding and fasting reduces cancer cell glucose utilization providing Snell dwarf mice with resistance to cancer. The elevation of circulating adiponectin, a hormone produced by adipose tissue, may contribute to the suppression of endogenous glucose production in 12 to 14 month-old Snell dwarf mice. We compared the incidence of cancer at time of death between old Snell dwarf and control mice. Only 18% of old Snell dwarf mice had malignant lesions at the time of death compared to 82% of control mice. The median ages at death for old Snell dwarf and control mice were 33 and 26 months, respectively. By contrast, previous studies showed a high incidence of cancer in old Ames dwarf mice at the time of death. Hence, resistance to cancer in old Snell dwarf mice may be mediated by neuroendocrine factors that reduce glucose utilization besides elevated adiponectin, reduced IGF-I and a lack of GH, PRL and TSH, seen in both Snell and Ames dwarf mice. Proteomics analysis of pituitary secretions from Snell dwarf mice confirmed the absence of GH and PRL, the secretion of ACTH and elevated secretion of Chromogranin B and Secretogranin II. Radioimmune assays confirmed that circulating Chromogranin B and Secretogranin II were elevated in 12 to 14 month-old Snell dwarf mice. In summary, our results in Snell dwarf mice suggest that the pituitary gland and adipose tissue are part of a neuroendocrine loop that lowers the risk of cancer during aging by reducing the availability of glucose.
PMCID: PMC2872123  PMID: 18582556
Glucose; Cancer; Adiponectin; Growth hormone; Dwarf mice; Pituitary; Chromogranins
7.  Endogenous glucose production is inhibited by the adipose-derived protein Acrp30 
Journal of Clinical Investigation  2001;108(12):1875-1881.
Intraperitoneal injection of purified recombinant Acrp30 lowers glucose levels in mice. To gain insight into the mechanism(s) of this hypoglycemic effect, purified recombinant Acrp30 was infused in conscious mice during a pancreatic euglycemic clamp. In the presence of physiological hyperinsulinemia, this treatment increased circulating Acrp30 levels by approximately twofold and stimulated glucose metabolism. The effect of Acrp30 on in vivo insulin action was completely accounted for by a 65% reduction in the rate of glucose production. Similarly, glucose flux through glucose-6-phosphatase (G6Pase) decreased with Acrp30, whereas the activity of the direct pathway of glucose-6-phosphate biosynthesis, an index of hepatic glucose phosphorylation, increased significantly. Acrp30 did not affect the rates of glucose uptake, glycolysis, or glycogen synthesis. These results indicate that an acute increase in circulating Acrp30 levels lowers hepatic glucose production without affecting peripheral glucose uptake. Hepatic expression of the gluconeogenic enzymes phosphoenolpyruvate carboxykinase and G6Pase mRNAs was reduced by more than 50% following Acrp30 infusion compared with vehicle infusion. Thus, a moderate rise in circulating levels of the adipose-derived protein Acrp30 inhibits both the expression of hepatic gluconeogenic enzymes and the rate of endogenous glucose production.
PMCID: PMC209474  PMID: 11748271

Results 1-7 (7)