Impact of overweight and obesity on epicardial adipose tissue in children with type 1 diabetes.

OBJECTIVES: Epicardial adipose tissue (EAT) thickness, a novel marker of cardiovascular disease (CVD), is increased in children with a healthy weight and type 1 diabetes (T1D). The prevalence of obesity has increased in children with T1D and may confer additional CVD risk. The purpose of this study was to examine EAT thickness in youth with and without T1D in the setting of overweight/obesity. METHODS: Youth with overweight/obesity and T1D (n=38) or without T1D (n=34) between the ages of 6-18 years were included in this study. Echocardiogram using spectral and color flow Doppler was used to measure EAT and cardiac function. Waist circumference, blood pressure, and HbA1c, were used to calculate estimated glucose disposal rate (eGDR) to estimate insulin resistance in children with T1D. RESULTS: EAT thickness was not significantly different in youth with T1D compared to controls (2.10 ± 0.67 mm vs. 1.90 ± 0.59 mm, p=0.19). When groups were combined, EAT significantly correlated with age (r=0.449, p≤0.001), BMI (r=0.538, p≤0.001), waist circumference (r=0.552, p≤0.001), systolic BP (r=0.247, p=0.036), myocardial performance index (r=-0.287, p=0.015), ejection fraction (r=-0.442, p≤0.001), and cardiac output index (r=-0.306, p=0.009). In the group with T1D, diastolic BP (r=0.39, p=0.02) and eGDR (r=-0.48, p=0.002) correlated with EAT. CONCLUSIONS: EAT was associated with measures of adiposity and insulin resistance but does not differ by diabetes status among youth with overweight/obesity. These findings suggest that adiposity rather than glycemia is the main driver of EAT thickness among youth with T1D.

Increase in the Number of Pediatric New-Onset Diabetes and Diabetic Ketoacidosis Cases During the COVID-19 Pandemic.

OBJECTIVE: Infection with SARS-CoV-2 induces a proinflammatory state that causes hyperglycemia and may precipitate diabetic ketoacidosis (DKA) in patients with known or new-onset diabetes. We examined the trends in new-onset diabetes and DKA prior to and following the onset of the COVID-19 pandemic. METHODS: This single-center retrospective observational study included pediatric patients (aged 0 to <18 years) hospitalized with new-onset type 1 diabetes or type 2 diabetes (T2D) before (March 1, 2018, to February 29, 2020) and after (March 1, 2020 to December 31, 2020) the pandemic onset. Demographic, anthropometrics, laboratory and clinical data, and outcomes were obtained. RESULTS: Among 615 children admitted with new-onset diabetes during the entire study period, 401 were admitted before the pandemic onset, and 214 were admitted after the pandemic onset. Children admitted with new-onset diabetes in the postpandemic period were significantly more likely to present with DKA (odds ratio, 1.76; 95% confidence interval, 1.24-2.52) than in the prepandemic phase. Children with DKA after the pandemic onset had higher lengths of hospitalization and were significantly more likely to experience severe DKA (odds ratio, 2.17; 95% confidence interval, 1.34-3.52). A higher proportion of children with DKA admitted to the pediatric intensive care unit required oxygen support after the pandemic onset than before the pandemic onset (8.85% vs 1.92%). Most cases of T2D with DKA occurred following the onset of the pandemic (62.5%). CONCLUSION: A significant increase in T2D cases occurred following the onset of the COVID-19 pandemic with a greater risk of DKA and severe ketoacidosis. Racial disparity was evident with a higher proportion of Black and American Indian children presenting with ketoacidosis following the pandemic onset.

Epicardial adipose thickness in youth with type 1 diabetes.

BACKGROUND AND OBJECTIVE: Epicardial adipose thickness (EAT) is increased in adults with type 1 diabetes (T1D) and is thought to contribute to cardiovascular disease (CVD) in this population. Given that CVD risk factors emerge early in life, the purpose of this study was to identify whether EAT is increased in pediatric patients with T1D compared with non-diabetic controls. METHODS: Anthropometric data, blood pressure (BP), and EAT were evaluated in 20 youth with T1D and 20 age, sex, and body mass index (BMI) matched healthy controls between the ages of 5 and 18 years. RESULTS: EAT was 18.5% higher among youth with T1D compared to healthy controls (1.65 ± 0.44 mm vs 1.37 ± 0.27 mm, P = .02). In the entire cohort, EAT was correlated with age (r = 0.71, P < .001), BMI (r = .69, P < .001), waist circumference (r = 0.60, P < .001), systolic BP (r = .34, P = .03), and diastolic BP (r = 0.41, P = .009). Among youth with T1D, there were no significant correlations between EAT and HbA1c (r = -0.16, P = .50), insulin dose (r = .09, P = .71), or duration of disease (r = 0.06, P = .82). CONCLUSIONS: Youth with T1D exhibited significantly higher EAT compared to controls. Increased EAT was associated with adiposity and BP, but not duration of disease, insulin dose, or glycemic control. Increased EAT may represent a pathophysiologic mechanism leading to premature CVD in pediatric patients with T1D.

Effect of severe obesity in childhood and adolescence on risk of type 2 diabetes in youth and early adulthood in an American Indian population.

OBJECTIVES: The risk of early-onset type 2 diabetes associated with the severity of obesity in youth is not well understood. This study aims to determine metabolic alterations and type 2 diabetes risk among American Indian children who are obese or severely obese. METHODS: Incidence rates of diabetes before 20 years (youth-onset) and 45 years were computed in 2728 children who were from 5 to <10 years and 4317 adolescents who were from 10 to <18 years without diabetes examined between 1965 and 2007. Obesity was defined as age-sex-adjusted body mass index (BMI) ≥95th percentile, and its severity was quantified as the percentage of the 95th percentile (%BMIp95 ). RESULTS: In the younger cohort, 0.9% of those non-obese and 2.9% of those with 100% to <120%BMIp95 had impaired glucose tolerance (IGT) compared to 8.6% of those with ≥140%BMIp95 . In the older cohort, 2.9% of those non-obese and 9.8% of those with 100% to <120%BMIp95 had IGT compared to 13.3% of those with ≥160%BMIp95 . The incidence of youth-onset diabetes was 3.8 and 4.9/1000 person-years in the child and adolescent cohorts, respectively, and before the age of 45 was 12.3 and 16.8/1000 person-years, respectively. Incidence rates of youth-onset diabetes in those with the most severe obesity (≥140%BMIp95 ) were 2.3 to 5.1 times as high as in those with the least severe obesity (100 to <120%BMIp95 ), and for onset of diabetes before the age of 45 were 1.6 to 2.2 times as high. CONCLUSIONS: Severe obesity in an American Indian population is a major driver of type 2 diabetes developing in adolescents and young adults.

Prion protein expression and functional importance in skeletal muscle.

UNLABELLED: Skeletal muscle expresses prion protein (PrP) that buffers oxidant activity in neurons. AIMS: We hypothesize that PrP deficiency would increase oxidant activity in skeletal muscle and alter redox-sensitive functions, including contraction and glucose uptake. We used real-time polymerase chain reaction and Western blot analysis to measure PrP mRNA and protein in human diaphragm, five murine muscles, and muscle-derived C2C12 cells. Effects of PrP deficiency were tested by comparing PrP-deficient mice versus wild-type mice and morpholino-knockdown versus vehicle-treated myotubes. Oxidant activity (dichlorofluorescin oxidation) and specific force were measured in murine diaphragm fiber bundles. RESULTS: PrP content differs among mouse muscles (gastrocnemius>extensor digitorum longus, EDL>tibialis anterior, TA; soleus>diaphragm) as does glycosylation (di-, mono-, nonglycosylated; gastrocnemius, EDL, TA=60%, 30%, 10%; soleus, 30%, 40%, 30%; diaphragm, 30%, 30%, 40%). PrP is predominantly di-glycosylated in human diaphragm. PrP deficiency decreases body weight (15%) and EDL mass (9%); increases cytosolic oxidant activity (fiber bundles, 36%; C2C12 myotubes, 7%); and depresses specific force (12%) in adult (8-12 mos) but not adolescent (2 mos) mice. INNOVATION: This study is the first to directly assess a role of prion protein in skeletal muscle function. CONCLUSIONS: PrP content varies among murine skeletal muscles and is essential for maintaining normal redox homeostasis, muscle size, and contractile function in adult animals.

Interleukin-1 stimulates catabolism in C2C12 myotubes.

Interleukin-1 (IL-1) is an inflammatory cytokine that has been linked to muscle catabolism, a process regulated by muscle-specific E3 proteins of the ubiquitin-proteasome pathway. To address cellular mechanism, we tested the hypothesis that IL-1 induces myofibrillar protein loss by acting directly on muscle to increase expression of two critical E3 proteins, atrogin1/muscle atrophy F-box (MAFbx) and muscle RING-finger 1 (MuRF1). Experiments were conducted using mature C2C12 myotubes to eliminate systemic cytokine effects and avoid paracrine signaling by nonmuscle cell types. Time-course protocols were used to define the sequence of cellular responses. We found that atrogin1/MAFbx mRNA and MuRF1 mRNA are elevated 60-120 min after myotube exposure to either IL-1alpha or IL-1beta. These responses are preceded by signaling events that promote E3 expression. Both IL-1 isoforms stimulate phosphorylation of p38 mitogen-activated protein kinase and stimulate nuclear factor-kappaB (NF-kappaB) signaling; I-kappaB levels fall and NF-kappaB DNA binding activity increases. Other regulators of E3 expression are unaffected by IL-1 [cytosolic oxidant activity, Forkhead-O (Foxo) activity] or respond paradoxically (AKT). Chronic exposure of C2C12 myotubes over 48 h resulted in reduced myotube width and loss of sarcomeric actin. We conclude that IL-1alpha and IL-1beta act via an oxidant- and AKT/Foxo-independent mechanism to activate p38 MAPK, stimulate NF-kappaB signaling, increase expression of atrogin1/MAFbx and MuRF1, and reduce myofibrillar protein in differentiated myotubes.

Stretch-stimulated glucose uptake in skeletal muscle is mediated by reactive oxygen species and p38 MAP-kinase.

Alternatives to the canonical insulin-stimulated pathway for glucose uptake are exercise- and exogenous reactive oxygen species (ROS)-stimulated glucose uptake. We proposed a model wherein mechanical loading, i.e. stretch, stimulates production of ROS to activate AMP-activated kinase (AMPK) to increase glucose uptake. Immunoblotting was used to measure protein phosphorylation; the fluorochrome probe 2'7'-dichlorofluorescin diacetate was used to measure cytosolic oxidant activity and 2-deoxy-d[1,2-(3)H]glucose was used to measure glucose uptake. The current studies demonstrate that stretch increases ROS, AMPKalpha phosphorylation and glucose transport in murine extensor digitorum longus (EDL) muscle (+121%, +164% and +184%, respectively; P < 0.05). We also demonstrate that stretch-induced glucose uptake persists in transgenic mice expressing an inactive form of the AMPKalpha2 catalytic subunit in skeletal muscle (+173%; P < 0.05). MnTBAP, a superoxide dismutase (SOD) mimetic, N-acteyl cysteine (NAC), a non-specific antioxidant, ebselen, a glutathione mimetic, or combined SOD plus catalase (ROS-selective scavengers) all decrease stretch-stimulated glucose uptake (P < 0.05) without changing basal uptake (P > 0.16). We also demonstrate that stretch-stimulated glucose uptake persists in the presence of the phosphatidylinositol 3-kinase (PI3-K) inhibitors wortmannin and LY294001 (P < 0.05) but is diminished by the p38-MAPK inhibitors SB203580 and A304000 (P > 0.99). These data indicate that stretch-stimulated glucose uptake in skeletal muscle is mediated by a ROS- and p38 MAPK-dependent mechanism that appears to be AMPKalpha2- and PI3-K-independent.

Physical inactivity and muscle weakness in the critically ill.

Patients in the intensive care unit commonly develop muscle weakness. In part, this reflects loss of mechanical loading due to physical inactivity, bed rest, or immobilization. Mechanical unloading stimulates a complex adaptive response that results in muscle atrophy and loss of specific force. One element of this response is slowing of protein synthesis, which is regulated by signaling pathways downstream of mammalian target of rapamycin and insulin-like growth factor-1. In parallel, protein degradation is accelerated via three coordinate processes: calcium-dependent proteolysis, adenosine triphosphate-dependent proteolysis, and lysosomal proteolysis. Finally, unloading stimulates apoptosis of a subset of myonuclei within multinucleated muscle fibers. This helps to stabilize the relationship between nuclear number and cell volume during atrophy. Each of these responses is promoted by concurrent development of oxidative stress caused by increased production of reactive oxygen species in unloaded muscle fibers. Countermeasures that lessen the effects of unloading include physical activity, nutritional supplements, hormone therapy, and antioxidant administration. Targeted research is needed to define the role of mechanical unloading in intensive care unit-associated weakness and develop countermeasures to preserve muscle function, lessen illness, and hasten the recovery of critically ill patients.

Acid Sphingomyelinase Deficiency Prevents Diet-induced Hepatic Triacylglycerol Accumulation and Hyperglycemia in Mice.

Acid sphingomyelinase plays important roles in ceramide homeostasis, which has been proposed to be linked to insulin resistance. To test this association in vivo, acid sphingomyelinase deletion (asm(-/-)) was transferred to mice lacking the low density lipoprotein receptor (ldlr(-/-)), and then offsprings were placed on control or modified (enriched in saturated fat and cholesterol) diets for 10 weeks. The modified diet caused hypercholesterolemia in all genotypes; however, in contrast to asm(+/+)/ldlr(-/-), the acid sphingomyelinase-deficient littermates did not display hepatic triacylglyceride accumulation, although sphingomyelin and other sphingolipids were substantially elevated, and the liver was enlarged. asm(-/-)/ldlr(-/-) mice on a modified diet did not accumulate body fat and were protected against diet-induced hyperglycemia and insulin resistance. Experiments with hepatocytes revealed that acid sphingomyelinase regulates the partitioning of the major fatty acid in the modified diet, palmitate, into two competitive and inversely related pools, triacylglycerides and sphingolipids, apparently via modulation of serine palmitoyltransferase, a rate-limiting enzyme in de novo sphingolipid synthesis. These studies provide evidence that acid sphingomyelinase activity plays an essential role in the regulation of glucose metabolism by regulating the hepatic accumulation of triacylglycerides and sphingolipids during consumption of a diet rich in saturated fats.

TNF induction of atrogin-1/MAFbx mRNA depends on Foxo4 expression but not AKT-Foxo1/3 signaling.

Murine models of starvation-induced muscle atrophy demonstrate that reduced protein kinase B (AKT) function upregulates the atrophy-related gene atrogin-1/MAFbx (atrogin). The mechanism involves release of inhibition of Forkhead transcription factors, namely Foxo1 and Foxo3. Elevated atrogin mRNA also corresponds with elevated TNF in inflammatory catabolic states, including cancer and chronic heart failure. Exogenous tumor necrosis factor (TNF) increases atrogin mRNA in vivo and in vitro. We used TNF-treated C2C12 myotubes to test the hypothesis that AKT-Foxo1/3 signaling mediates TNF regulation of atrogin mRNA. Here we confirm that exposure to TNF increases atrogin mRNA (+125%). We also confirm that canonical AKT-mediated regulation of atrogin is active in C2C12 myotubes. Inhibition of phosphoinositol-3 kinase (PI3K)/AKT signaling with wortmannin reduces AKT phosphorylation (-87%) and increases atrogin mRNA (+340%). Activation with insulin-like growth factor (IGF) increases AKT phosphorylation (+126%) and reduces atrogin mRNA (-15%). Although AKT regulation is intact, our data suggest it does not mediate TNF effects on atrogin. TNF increases AKT phosphorylation (+50%) and stimulation of AKT with IGF does not prevent TNF induction of atrogin mRNA. Nor does TNF appear to signal through Foxo1/3 proteins. TNF has no effect on Foxo1/3 mRNA or Foxo1/3 nuclear localization. Instead, TNF increases nuclear Foxo4 protein (+55%). Small interfering RNA oligos targeted to two distinct regions of Foxo4 mRNA reduce the TNF-induced increase in atrogin mRNA (-34% and -32%). We conclude that TNF increases atrogin mRNA independent of AKT via Foxo4. These results suggest a mechanism by which inflammatory catabolic states may persist in the presence of adequate growth factors and nutrition.