The American journal of clinical nutrition
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Review
Regulation of skeletal muscle mitochondrial fatty acid metabolism in lean and obese individuals.
A reduction in fatty acid (FA) oxidation has been associated with lipid accumulation and insulin resistance in skeletal muscle of obese individuals. Numerous reports suggest that the reduction in FA oxidation may result from intrinsic mitochondrial defects, although little direct evidence has been offered to support this conclusion. This brief review summarizes recent work from our laboratory that reexamined whether this decrease in skeletal muscle FA oxidation with obesity was attributable to a dysfunction in FA oxidation within mitochondria or simply to a reduction in muscle mitochondrial content. ⋯ However, this did not result from decreased protein contents of various transcription factors, because peroxisome proliferater-activated receptor gamma coactivator 1alpha (PGC1alpha), PGC1beta, peroxisome proliferator-activated receptor alpha (PPARalpha), and mitochondrial transcription factor A (TFAM) were not reduced with obesity. In contrast, it appears that obesity is associated with altered regulation of cofactors (PGC1alpha and PGC1beta) and their downstream transcription factors (PPARalpha, PPARdelta/beta, and TFAM), because relations among these variables were present in muscle from lean individuals but not from obese individuals. These findings imply that obese individuals would benefit from interventions that increase the skeletal muscle mitochondrial content and the potential for oxidizing FAs.
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Randomized Controlled Trial
Sleep curtailment is accompanied by increased intake of calories from snacks.
Short sleep is associated with obesity and may alter the endocrine regulation of hunger and appetite. ⋯ Recurrent bedtime restriction can modify the amount, composition, and distribution of human food intake, and sleeping short hours in an obesity-promoting environment may facilitate the excessive consumption of energy from snacks but not meals.
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Randomized Controlled Trial
Oral glutamine increases circulating glucagon-like peptide 1, glucagon, and insulin concentrations in lean, obese, and type 2 diabetic subjects.
Incretin hormones, such as glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), play an important role in meal-related insulin secretion. We previously demonstrated that glutamine is a potent stimulus of GLP-1 secretion in vitro. ⋯ Glutamine effectively increases circulating GLP-1, GIP, and insulin concentrations in vivo and may represent a novel therapeutic approach to stimulating insulin secretion in obesity and type 2 diabetes.
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Randomized Controlled Trial Multicenter Study
Estimation of the dietary requirement for vitamin D in healthy adults.
Knowledge gaps have contributed to considerable variation among international dietary recommendations for vitamin D. ⋯ The range of vitamin D intakes required to ensure maintenance of wintertime vitamin D status [as defined by incremental cutoffs of serum 25(OH)D] in the vast majority (>97.5%) of 20-40-y-old adults, considering a variety of sun exposure preferences, is between 7.2 and 41.1 microg/d.