Effects of maternal exercise on infant mesenchymal stem cell mitochondrial function, insulin action, and body composition in infancy

Maternal exercise (ME) has been established as a useful non-pharmacological intervention to improve infant metabolic health; however, mechanistic insight behind these adaptations remains mostly confined to animal models. Infant mesenchymal stem cells (MSCs) give rise to infant tissues (e.g., skeletal muscle), and remain involved in mature tissue maintenance. Importantly, these cells maintain metabolic characteristics of an offspring donor and provide a model for the investigation of mechanisms behind infant metabolic health improvements. We used undifferentiated MSC to investigate if ME affects infant MSC mitochondrial function and insulin action, and if these adaptations are associated with lower infant adiposity. We found that infants from exercising mothers have improvements in MSC insulin signaling related to higher MSC respiration and fat oxidation, and expression and activation of energy-sensing and redox-sensitive proteins. Further, we found that infants exposed to exercise in utero were leaner at 1 month of age, with a significant inverse correlation between infant MSC respiration and infant adiposity at 6 months of age. These data suggest that infants from exercising mothers are relatively leaner, and this is associated with higher infant MSC mitochondrial respiration, fat use, and insulin action.

Differences in substrate metabolism between African American and Caucasian infants: evidence from mesenchymal stem cells

Type 2 diabetes is more prevalent in African American (AA) than Caucasian (C) adults. Further, differential substrate utilization has been observed between AA and C adults, but data regarding metabolic differences between races at birth remains scarce. The purpose of the present study was to determine if there are racial differences in substrate metabolism evident at birth utilizing mesenchymal stem cells (MSCs) collected from offspring umbilical cords. Using radio-labeled tracers, MSCs from offspring of AA and C mothers were tested for glucose and fatty acid metabolism in the undifferentiated state and while undergoing myogenesis in vitro. Undifferentiated MSCs from AA exhibited greater partitioning of glucose towards non-oxidized glucose metabolites. In the myogenic state, AA displayed higher glucose oxidation, but similar fatty acid oxidation rates. In the presence of both glucose and palmitate, but not palmitate only, AA exhibit a higher rate of incomplete fatty acid oxidation evident by a greater production of acid soluble metabolites. Myogenic differentiation of MSCs elicited an increase in glucose oxidation in AA, but not in C. Together, these data suggest that metabolic differences between AA and C races may exist at birth.

Obestatin and ghrelin in obese and in pregnant women

We identified, through qPCR, receptor mRNA for a number of gut peptides in female human omental fat: the incretins, GIP and GLP-1, the orexigenic peptides PYY-Y1 and -Y2 and ghrelin, and the anorexigenic peptide obestatin. Four cohorts of women were examined: lean controls (BMI<23), obese (BMI>41), obese diabetic and term pregnant women. Human fat expressed receptor mRNAs for all six peptides. Pregnant women expressed roughly three times as much orphan GPR-39 receptor, a proposed obestatin receptor, than other women and less than half as much of the ghrelin receptor (GHSR-1a). An immunoblot probed with a GPR-39 selective antibody yielded a single band corresponding to the correct molecular weight (52 kDa) for the proposed obestatin receptor. Fluorescent immunohistochemistry of human fat employing the same antibody indicated the receptor protein was localized to the adipocyte cell membrane. The concentration of obestatin circulating in blood was measured in the same cohort of women and was significantly lower in obese and obese diabetic women compared to control.

Retroviral infection can abrogate the factor-dependency of hematopoietic cells by autocrine and non-autocrine mechanisms depending on the presence of a functional viral oncogene

The mechanisms responsible for abrogation of the growth factor-dependency of a hematopoietic cell line were investigated. FDC-P1 cells were infected with retroviral constructs containing the neo gene and either a wild-type or a temperature-sensitive v-src oncogene. v-srcwt abrogated the factor-dependency of these cells since each G418r colony gave rise to factor-independent cells and no autocrine growth factor activity was detected. Moreover, the vast majority (< 99%) of cells infected with the v-srcts mutant gave rise to conditional factor-independent cells. Therefore a functional v-src gene product was required for growth factor-independence which occurred by a non-autocrine mechanism. A minority of factor-independent cells which arose after v-srcts infection, grew at the non-permissive temperature and one-half secreted granulocyte/macrophage-colony stimulating factor (GM-CSF) which supports the growth of the parental cells. Since the v-srcts viral stock contained a helper virus, Murine Leukemia Virus (MuLV), the ability of this virus to relieve factor-dependency was examined. A low frequency of factor-independent transformants was recovered after MuLV infection and one-half secreted GM-CSF. Therefore, retroviruses such as MuLV which lack an oncogene, can transform cells by stimulating autocrine growth factor secretion. Subsequent experiments performed with helper-free v-src preparations indicated that they could abrogate factor-dependency directly by a non-autocrine mechanism. These results demonstrate that a hematopoietic cell line can be transformed by two different mechanisms after retroviral infection and may be relevant for understanding hematopoietic cell transformation after persistent viral infection.