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ABSTRACT: Insulin is as a major postprandial hormone with profound effects on carbohydrate, fat, and protein metabolism. In the absence of exogenous insulin, patients with type 1 diabetes exhibit a variety of metabolic abnormalities including hyperglycemia, glycosurea, accelerated ketogenesis, and muscle wasting due to increased proteolysis. We analyzed plasma from type 1 diabetic (T1D) humans during insulin treatment (I+) and acute insulin deprivation (I-) and non-diabetic participants (ND) by (1)H nuclear magnetic resonance spectroscopy and liquid chromatography-tandem mass spectrometry. The aim was to determine if this combination of analytical methods could provide information on metabolic pathways known to be altered by insulin deficiency. Multivariate statistics differentiated proton spectra from I- and I+ based on several derived plasma metabolites that were elevated during insulin deprivation (lactate, acetate, allantoin, ketones). Mass spectrometry revealed significant perturbations in levels of plasma amino acids and amino acid metabolites during insulin deprivation. Further analysis of metabolite levels measured by the two analytical techniques indicates several known metabolic pathways that are perturbed in T1D (I-) (protein synthesis and breakdown, gluconeogenesis, ketogenesis, amino acid oxidation, mitochondrial bioenergetics, and oxidative stress). This work demonstrates the promise of combining multiple analytical methods with advanced statistical methods in quantitative metabolomics research, which we have applied to the clinical situation of acute insulin deprivation in T1D to reflect the numerous metabolic pathways known to be affected by insulin deficiency.
PLoS ONE 01/2010; 5(5):e10538. · 4.09 Impact Factor
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ABSTRACT: Reductions in insulin sensitivity in conjunction with muscle mitochondrial dysfunction have been reported to occur in many conditions including aging. The objective was to determine whether insulin resistance and mitochondrial dysfunction are directly related to chronological age or are related to age-related changes in body composition.
Twelve young lean, 12 young obese, 12 elderly lean, and 12 elderly obese sedentary adults were studied. Insulin sensitivity was measured by a hyperinsulinemic-euglycemic clamp, and skeletal muscle mitochondrial ATP production rates (MAPRs) were measured in freshly isolated mitochondria obtained from vastus lateralis biopsy samples using the luciferase reaction.
Obese participants, independent of age, had reduced insulin sensitivity based on lower rates of glucose infusion during a hyperinsulinemic-euglycemic clamp. In contrast, age had no independent effect on insulin sensitivity. However, the elderly participants had lower muscle MAPRs than the young participants, independent of obesity. Elderly participants also had higher levels inflammatory cytokines and total adiponectin. In addition, higher muscle MAPRs were also noted in men than in women, whereas glucose infusion rates were higher in women.
The results demonstrate that age-related reductions in insulin sensitivity are likely due to an age-related increase in adiposity rather than a consequence of advanced chronological age. The results also indicate that an age-related decrease in muscle mitochondrial function is neither related to adiposity nor insulin sensitivity. Of interest, a higher mitochondrial ATP production capacity was noted in the men, whereas the women were more insulin sensitive, demonstrating further dissociation between insulin sensitivity and muscle mitochondrial function.
Diabetes 10/2009; 59(1):89-97. · 8.29 Impact Factor
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ABSTRACT: Retinol binding protein 4 (RBP4) levels are elevated in insulin-resistant states and reduced in type 1 diabetes (T1D), but it is unknown whether changes in insulin levels and glycemic control alter RBP4 levels. In vivo synthesis rates of RBP4 and their relationship to RBP4 levels remain to be determined.
The aim of the study was to determine whether the synthesis rate of RBP4 is altered in people with T1D during both insulin deficiency and insulin treatment.
Seven T1D participants were studied on two occasions, during 8 h of insulin deprivation and during insulin treatment, and compared with nondiabetic (ND) controls.
We measured in vivo fractional synthesis rate of RBP4 using [ring-(13)C(6)]phenylalanine as a tracer and RBP4 concentration in plasma by nephelometric assay and Western blot analyses.
Plasma RBP4 levels were lower (P < 0.01) in insulin-treated T1D than in ND but were not different between insulin-deprived T1D and ND participants. Synthesis rates of RBP4 in ND (2.46 +/- 0.29%/h) were higher than in insulin-treated T1D (1.45 +/- 0.21) (P = 0.02), but there was no difference between ND and insulin-deprived T1D (2.24 +/- 0.24). Glucose levels were not different between ND and insulin-treated T1D, but insulin levels were higher in insulin-treated T1D (82.8 +/- 2 pmol/liter) than in ND (28.7 +/- 6) and insulin-deprived T1D (4.6 +/- 1.6) (P < 0.01).
Insulin treatment that achieved normoglycemia but relative hyperinsulinemia was associated with lower RBP4 synthesis and levels in T1D. Short-term insulin deprivation and hyperglycemia had no effect on RBP4 levels and synthesis rates in T1D.
The Journal of clinical endocrinology and metabolism 10/2009; 94(12):5125-30. · 6.50 Impact Factor
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ABSTRACT: It remains to be determined whether systemic insulin replacement normalizes synthesis rates of different plasma proteins and whether there are differential effects on various plasma proteins. We tested a hypothesis that insulin deprivation differentially affects individual plasma protein synthesis and that systemic insulin treatment may not normalize synthesis of all plasma proteins. We measured synthesis rates of 41 plasma proteins in seven each of type 1 diabetic (T1DM) and nondiabetic participants (ND) using [ring-(13)C(6)]phenylalanine as a tracer. T1DM were studied while on chronic insulin treatment and during 8 h insulin deprivation. Insulin treatment normalized glucose levels, but plasma insulin levels were higher during insulin treatment than during insulin deprivation in T1DM and ND. Individual plasma proteins were purified by affinity chromatography and two-dimensional gel electrophoresis. Only 41 protein gel spots from over 300 were chosen based on their protein homogeneity. Insulin deprivation and hyperglycemia either significantly increased (n = 12) or decreased (n = 12) synthesis rates of 24 of 41 plasma proteins in T1DM compared with ND. Insulin treatment normalized synthesis rates of 13 of these 24 proteins, which were altered during insulin deprivation. However, insulin treatment significantly altered the synthesis of 14 additional proteins. In conclusion, acute insulin deprivation caused both a decrease and increase in synthesis rates of many plasma proteins with various functions. Moreover, chronic systemic insulin treatment not only did not normalize synthesis of all plasma proteins but also altered synthesis of several additional proteins that were unaltered during insulin deprivation.
AJP Endocrinology and Metabolism 09/2009; 297(4):E889-97. · 4.75 Impact Factor
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ABSTRACT: Muscle mitochondrial dysfunction occurs in many insulin-resistant states, such as type 2 diabetes, prompting a hypothesis that mitochondrial dysfunction may cause insulin resistance. We determined the impact of insulin deficiency on muscle mitochondrial ATP production by temporarily depriving type 1 diabetic patients of insulin treatment.
We withdrew insulin for 8.6 +/- 0.6 h in nine C-peptide-negative type 1 diabetic subjects and measured muscle mitochondrial ATP production and gene transcript levels (gene array and real-time quantitative PCR) and compared with insulin-treated state. We also measured oxygen consumption (indirect calorimetry); plasma levels of glucagon, bicarbonate, and other substrates; and urinary nitrogen.
Withdrawal of insulin resulted in increased plasma glucose, branched chain amino acids, nonesterified fatty acids, beta-hydroxybutyrate, and urinary nitrogen but no change in bicarbonate. Insulin deprivation decreased muscle mitochondrial ATP production rate (MAPR) despite an increase in whole-body oxygen consumption and altered expression of many muscle mitochondrial gene transcripts. Transcript levels of genes involved in oxidative phosphorylation were decreased, whereas those involved in vascular endothelial growth factor (VEGF) signaling, inflammation, cytoskeleton signaling, and integrin signaling pathways were increased.
Insulin deficiency and associated metabolic changes reduce muscle MAPR and expression of oxidative phosphorylation genes in type 1 diabetes despite an increase in whole-body oxygen consumption. Increase in transcript levels of genes involved in VEGF, inflammation, cytoskeleton, and integrin signaling pathways suggest that vascular factors and cell proliferation that may interact with mitochondrial changes occurred.
Diabetes 12/2007; 56(11):2683-9. · 8.29 Impact Factor
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ABSTRACT: A case of granulomatous slack skin disease is presented in which we studied the possible involvement of extrarenal 1,25(OH)2D in the pathogenesis of the patient's hypercalcemia. Immunolocalization of 1alpha-OH in skin showed simultaneous dysregulation in epithelial and granulomatous cells.
Granuloma-forming diseases such as sarcoidosis are associated with extrarenal synthesis of active 1,25-dihydroxyvitamin D [1,25(OH)2D]. Here we describe a case of granulomatous slack skin disease in which we have studied the possible involvement of extrarenal synthesis of 1,25(OH)2D in the pathogenesis of the patient's hypercalcemia. The aim of the study was to clarify the etiology of hypercalcemia in this patient.
This was a case study of a 19-year-old man with a T-cell lymphoproliferative disorder diagnosed as granulomatous slack skin disease who presented with hypercalcemia and raised serum 1,25(OH)2D. Analysis of expression of the enzyme 25-hydroxyvitamin D 1alpha-hydroxylase (1alpha-hydroxylase), which catalyzes synthesis of 1,25(OH)2D, was carried out by immunohistochemical analysis of involved and uninvolved skin. Approval was granted by the Mayo Foundation Institutional Review Board and Biospecimens Subcommittee.
In uninvolved skin, expression of 1alpha-hydroxylase was confined to the basal layer of the epidermis, whereas slack skin showed overexpression of the enzyme in dermal granulomata and basal cells of the epidermis.
Hypercalcemia associated with granulomatous slack skin syndrome seems to be caused by dysregulation of 1alpha-hydroxylase expression in both epidermal and dermal granulomatous cells. This contrasts with psoriasis and sarcoidosis of the skin, in which overexpression of the enzyme is restricted to keratinocytes and granulomata, respectively.
Journal of Bone and Mineral Research 10/2006; 21(9):1496-9. · 6.37 Impact Factor
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ABSTRACT: Sarcopenia contributes significantly to the morbidity, decrease in quality of life, and health care costs in the elderly. It is characterized by a decrease in muscle mass and strength, starting as early as the fourth decade of life in humans. Distinct muscle changes include a decrease in type 2 muscle fibers and a decrease in myosin heavy chains IIa and IIx mRNA levels. In addition, a decrease in whole body protein turnover, mixed muscle protein synthesis, myosin heavy chain synthesis, and mitochondrial protein synthesis have been reported. Different tissues and organs display different responses to aging, with more oxidative tissue generally having more age-related changes. Exercise has been shown to increase strength, aerobic capacity, and muscle protein synthesis, as well as to increase muscle mitochondrial enzyme activity in both young and older people; however, exercise does not reverse all age-related changes. The metabolic effects of sarcopenia include a decrease in resting metabolic rate secondary to decreased fat-free mass and decreased physical activity, leading to a higher prevalence of insulin resistance, type 2 diabetes mellitus, dyslipidemia, and hypertension. The way in which age-related changes in hormone levels affect muscle remains to be fully understood. The effect of replacing those hormones on sarcopenia has led to some conflicting results, but further investigations are ongoing.
Current Topics in Developmental Biology 02/2005; 68:123-48. · 6.00 Impact Factor
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ABSTRACT: Cytomegalovirus (CMV) pneumonia can be a life-threatening disease in immunocompromised patients such as transplant recipients and patients given immunosuppressive therapy. Although CMV infections are highly prevalent in the general population, symptomatic pneumonia in an immunocompetent adult has been documented rarely. We describe a 47-year-old male smoker who presented with a 3.5-cm cavitary mass in the upper lobe of the left lung, highly suggestive of lung cancer. Wedge resection of the mass on thoracotomy revealed CMV pneumonia with no evidence of malignancy or other infections. No antiviral therapy was given to this immunocompetent patient, and no additional manifestations of CMV disease occurred.
Mayo Clinic Proceedings 05/2003; 78(4):488-90. · 5.70 Impact Factor
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Endocrine Practice 12(6):699. · 2.49 Impact Factor
