Clinton Elfers

Vitamin D deficiency in obese rats exacerbates nonalcoholic fatty liver disease and increases hepatic resistin and toll‐like receptor activation

Childhood obesity is associated with type 2 diabetes mellitus and nonalcoholic fatty liver disease (NAFLD). Recent studies have found associations between vitamin D deficiency (VDD), insulin resistance (IR), and NAFLD among overweight children. To further explore mechanisms mediating these effects, we fed young (age 25 days) Sprague‐Dawley rats with a low‐fat diet (LFD) alone or with vitamin D depletion (LFD+VDD). A second group of rats was exposed to a Westernized diet (WD: high‐fat/high‐fructose corn syrup) that is more typically consumed by overweight children, and was either replete (WD) or deficient in vitamin D (WD+VDD). Liver histology was assessed using the nonalcoholic steatohepatitis (NASH) Clinical Research Network (CRN) scoring system and expression of genes involved in inflammatory pathways were measured in liver and visceral adipose tissue after 10 weeks. In VDD groups, 25‐OH‐vitamin D levels were reduced to 29% (95% confidence interval [CI]: 23%‐36%) compared to controls. WD+VDD animals exhibited significantly greater hepatic steatosis compared to LFD groups. Lobular inflammation as well as NAFLD Activity Score (NAS) were higher in WD+VDD versus the WD group (NAS: WD+VDD 3.2 ± 0.47 versus WD 1.50 ± 0.48, P < 0.05). Hepatic messenger RNA (mRNA) levels of Toll‐like receptors (TLR)2, TLR4, and TLR9, as well as resistin, interleukins (IL)‐1β, IL‐4, and IL‐6 and oxidative stress marker heme oxygenase (HO)‐1, were higher in WD+VDD versus WD animals (P < 0.05). Logistic regression analyses showed significant associations between NAS score and liver mRNA levels of TLRs 2, 4, and 9, endotoxin receptor CD14, as well as peroxisome proliferator activated receptor (PPAR)γ, and HO‐1. Conclusion: VDD exacerbates NAFLD through TLR‐activation, possibly by way of endotoxin exposure in a WD rat model. In addition it causes IR, higher hepatic resistin gene expression, and up‐regulation of hepatic inflammatory and oxidative stress genes. (HEPATOLOGY 2012)

Vitamin d deficiency in obese children and its relationship to insulin resistance and adipokines.

Low-serum concentrations of 25-hydroxyvitamin D [25(OH)D] are associated with insulin resistance in adults. Less data are available in pediatric populations. Serum 25(OH)D serum concentrations were assessed in 125 obese and 31 nonobese children (age 11.9 ± 2.7 y, range 6–16 y, 49% male) living in Bonn, Germany. The relationship between 25(OH)D, measured by liquid chromatography-tandem mass spectrometry, and measures of insulin sensitivity and adipokines adiponectin and resistin were analyzed. Seventy-six % of subjects were 25(OH)D deficient (<20 ng/mL). Higher insulin, homeostasis model assessment-insulin resistance (HOMA-IR r = −0.269, P = 0.023), and hemoglobin A1c (HbA1c) as well as lower quantitative insulin-sensitivity check index (QUICKI r = 0.264, P = 0.030) values were found in obese children with lower 25(OH)D concentrations even after adjustment for gender, age, and body mass index. Furthermore, 25(OH)D correlated significantly with adiponectin, but not with resistin. Our results suggest that hypovitaminosis D is a risk factor for developing insulin resistance independent of adiposity.

Reduced adiponectin signaling due to weight gain results in nonalcoholic steatohepatitis through impaired mitochondrial biogenesis

Obesity and adiponectin depletion have been associated with the occurrence of nonalcoholic fatty liver disease (NAFLD). The goal of this study was to identify the relationship between weight gain, adiponectin signaling, and development of nonalcoholic steatohepatitis (NASH) in an obese, diabetic mouse model. Leptin‐receptor deficient (Leprdb/db) and C57BL/6 mice were administered a diet high in unsaturated fat (HF) (61%) or normal chow for 5 or 10 weeks. Liver histology was evaluated using steatosis, inflammation, and ballooning scores. Serum, adipose tissue, and liver were analyzed for changes in metabolic parameters, messenger RNA (mRNA), and protein levels. Leprdb/db HF mice developed marked obesity, hepatic steatosis, and more than 50% progressed to NASH at each timepoint. Serum adiponectin level demonstrated a strong inverse relationship with body mass (r = −0.82; P < 0.0001) and adiponectin level was an independent predictor of NASH (13.6 μg/mL; P < 0.05; area under the receiver operating curve (AUROC) = 0.84). White adipose tissue of NASH mice was characterized by increased expression of genes linked to oxidative stress, macrophage infiltration, reduced adiponectin, and impaired lipid metabolism. HF lepr db/db NASH mice exhibited diminished hepatic adiponectin signaling evidenced by reduced levels of adiponectin receptor‐2, inactivation of adenosine monophosphate activated protein kinase (AMPK), and decreased expression of genes involved in mitochondrial biogenesis and β‐oxidation (Cox4, Nrf1, Pgc1α, Pgc1β and Tfam). In contrast, recombinant adiponectin administration up‐regulated the expression of mitochondrial genes in AML‐12 hepatocytes, with or without lipid‐loading. Conclusion: Leprdb/db mice fed a diet high in unsaturated fat develop weight gain and NASH through adiponectin depletion, which is associated with adipose tissue inflammation and hepatic mitochondrial dysfunction. We propose that this murine model of NASH may provide novel insights into the mechanism for development of human NASH. (Hepatology 2014;60:133–145)

Irisin and its relation to insulin resistance and puberty in obese children: a longitudinal analysis.

CONTEXT Irisin is a recently identified myokine affecting metabolic and glucose homeostasis. However, the role of irisin in obesity and its metabolic consequences are controversial, and data in children are scarce. OBJECTIVE To study the relationships between irisin, insulin resistance, and puberty before and after weight loss in obese children with and without impaired glucose tolerance. DESIGN One-year follow-up study in obese children participating in a lifestyle intervention. SETTING Primary care. PATIENTS Forty obese children and 20 normal-weight children of similar age, gender, and pubertal stage. INTERVENTION A 1-year outpatient intervention program based on exercise, behavior, and nutrition therapy. MAIN OUTCOMES MEASURES Fasting serum irisin, weight status (body mass index [BMI] SD score), and the following parameters of the metabolic syndrome: insulin resistance index (homeostasis model of assessment), blood pressure, and lipids. RESULTS The irisin levels were the highest in obese children with impaired glucose tolerance, followed by obese children with normal glucose tolerance, and levels were lowest in normal-weight children (P < .001). In a multiple linear regression analysis, baseline irisin was significantly associated with pubertal stage, high-density lipoprotein-cholesterol, and homeostasis model of assessment, but not to age, gender, BMI, or any other parameter of the metabolic syndrome. The irisin concentrations were significantly (P = .010) lower in the prepubertal compared to the pubertal children. In longitudinal analyses, changes of irisin were significantly associated with entry into puberty, change of fasting glucose, and 2-hour glucose in an oral glucose tolerance test, but not with change of BMI or any other parameter. CONCLUSIONS Irisin levels are related to pubertal stage and insulin resistance but not to weight status in childhood.

Brain-derived neurotrophic factor and its relation to leptin in obese children before and after weight loss

OBJECTIVE Brain-derived neurotrophic factor (BDNF) is a regulator of energy homeostasis and food intake through hypothalamic signaling. Currently, data regarding BDNF in children with obesity are lacking. We evaluated serum BDNF concentrations in obese children, both before and after lifestyle intervention, in reference to those of lean children. METHODS A total of 90 (24 normal weight; 66 obese) children were studied utilizing a cross-sectional clinical outpatient study design. In addition, longitudinal data analysis was performed in 30 obese children participating in a lifestyle intervention for one year. RESULTS Fasting serum BDNF concentrations were higher in obese vs. normal weight children (BDNF 20.3±1.0 vs. 12.5±1.7 ng/mL, respectively, mean±SEM, p<0.001) and correlated significantly to BMI standard deviation score (r=0.426, p<0.001), and leptin (r=0.414, p<0.01). BDNF concentrations were not regulated in response to food, 60 min after ingestion of a liquid test meal. After one year lifestyle intervention, delta BDNF correlated significantly to delta leptin (r=0.475, p<0.01), but not to changes of insulin resistance index HOMA-IR, systolic and diastolic blood pressure, HDL, LDL, and triglycerides. In a multiple stepwise linear regression adjusted for pubertal stage, age, sex, and BMI, delta BDNF correlated significantly (p<0.05) to delta leptin and delta triceps skinfold and in tendency to delta subscapularis skinfold thickness (p=0.050). CONCLUSIONS Our results in children do not indicate a significant relationship between BDNF and insulin resistance or cardiovascular risk factors. However, the correlation between changes of BDNF and changes of leptin suggests a relationship between BDNF and fat mass.

Semiquantitative analysis of hypothalamic damage on MRI predicts risk for hypothalamic obesity

Excessive weight gain frequently occurs in patients with hypothalamic tumors and lesions leading to hypothalamic obesity (HO).

Effects of methylphenidate on weight gain and food intake in hypothalamic obesity

For patients with a craniopharyngioma (CP), treatment of hypothalamic obesity (HO) and hyperphagia following resection and/or radiotherapy is extremely difficult and few reports have been published on potential drug therapies. Psychomotor stimulant methylphenidate (MPH) has been reported to inhibit food intake (FI). In this paper, we report reduction of body mass index (BMI) and appetite in an adolescent CP patient suffering from HO. We then tested the ability of MPH to attenuate the FI and body weight (BW) gain in a rat model consistent with the neuroanatomical and metabolic disturbances commonly observed in obese CP patients. Specifically, we used a novel electrolytically generated combined medial hypothalamic lesion (CMHL) affecting the arcuate nucleus, ventromedial hypothalamic nucleus, and dorsomedial hypothalamic nucleus to induce hyperphagia, rapid weight gain, and adiposity. Both CMHL and control animals (n = 7 per group) were administered either methylphenidate HCl (MPH; 20 mg kg−1 day−1) or saline for 4 days in a crossover design experiment 28 weeks post-surgery. A significant decrease in percent baseline FI (CMHL −23%, p = 0.008; control −20%, p = 0.002) and percent change in BW (CMHL −1.97%/4 days, p = 0.011; control −1.75%/4 days, p = 0.003) was observed during MPH treatment as compared to saline. Conclusion: This study shows MPH treatment of severely obese CMHL rats resulted in significantly reduced FI and BW loss.

A Novel Rodent Model That Mimics the Metabolic Sequelae of Obese Craniopharyngioma Patients

Patients with craniopharyngioma (CP), a tumor located in the pituitary and/or hypothalamus, are susceptible to developing obesity and many metabolic complications. The study aim was to create a rodent model that mimics the complex neuroanatomical and metabolic disturbances commonly seen in obese CP patients. We compared the metabolic phenotype of animals with three distinct types of hypothalamic lesions: 1) destruction of the arcuate nucleus (ARC) induced by monosodium glutamate (MSG), 2) electrolytic lesion of the adjacent ventromedial nucleus (VMN) alone, 3) both the VMN and dorsomedial nucleus (DMN), or a 4) combined medial hypothalamic lesion (CMHL) affecting the VMN, DMN, and the ARC. Only the CMHL model exhibited all key features observed in patients with hypothalamic obesity induced by CP. These features included excessive weight gain due to increased adiposity, increased food intake, and pronounced hyperinsulinemia and hyperleptinemia. Similar to characteristics of patients with CP, CMHL animals exhibited reduced plasma levels of alpha-melanocyte stimulating hormone and reduced ambulatory activity compared with weight-matched controls. Therefore, the CMHL model best mimics the complex metabolic abnormalities observed in obese CP patients compared with lesions to other hypothalamic areas and provides a foundation for future pharmacological approaches to treat obesity in children with hypothalamic damage.

Pediatric Central Diabetes Insipidus: Brain Malformations Are Common and Few Patients Have Idiopathic Disease

CONTEXT Pediatric cohorts of central diabetes insipidus (CDI) have shown varying prevalences for the different causes of CDI, including idiopathic. OBJECTIVE The objective of the study was to determine the causes of CDI at a pediatric tertiary care center and to characterize their clinical outcomes. DESIGN AND SETTING All patients with CDI at Seattle Childrens Hospital were identified and retrospectively analyzed. PATIENTS From 2000 to 2013, 147 patients with CDI were encountered (mean age 7 y at diagnosis, mean follow-up 6.2 y). OUTCOME MEASURES The different causes of CDI were grouped, and age of diagnosis, anterior pituitary hormone deficiencies (APHDs), and presence of the posterior pituitary bright spot (PPBS) were analyzed. Patients with idiopathic CDI had infundibular thickening measured using a systematic method. RESULTS Brain malformations caused 24% of CDI cases, and 12.2% were idiopathic. Four of 22 patients with initially idiopathic CDI were diagnosed with an underlying condition, none occurring later than 2.5 years from diagnosis. APHDs were as common in the brain malformation group as they were in the tumor/infiltrative group (72% vs 85%; P = .09). The PPBS was present in at least 13% of patients and in 19% of those with brain malformations. Patients with idiopathic CDI and stalk thickening on the initial magnetic resonance imaging were more likely to have an underlying diagnosis (40% vs 0%; P = .03). CONCLUSIONS Brain malformations were a more common cause of pediatric CDI than previously reported. These patients have a high rate of APHDs, and many have persistence of the PPBS. Idiopathic CDI is an uncommon diagnosis, and none of our patients were diagnosed with Langerhans cell histiocytosis or germinoma for more than 3 years from CDI diagnosis. Providers can consider less frequent magnetic resonance imaging after this time point. A systematic method of infundibular measurement on the initial magnetic resonance imaging may predict an underlying germinoma or Langerhans cell histiocytosis.

Vitamin B12 Conjugation of Peptide-YY3–36 Decreases Food Intake Compared to Native Peptide-YY3–36 Upon Subcutaneous Administration in Male Rats

Challenges to peptide-based therapies include rapid clearance, ready degradation by hydrolysis/proteolysis, and poor intestinal uptake and/or a need for blood brain barrier transport. This work evaluates the efficacy of conjugation of vitamin B12 (B12) on sc administered peptide tyrosine tyrosine (PYY)(3-36) function. In the current experiments, a B12-PYY(3-36) conjugate was tested against native PYY(3-36), and an inactive conjugate B12-PYYC36 (null control) in vitro and in vivo. In vitro experiments demonstrated similar agonism for the neuropeptide Y2 receptor by the B12-PYY(3-36) conjugate (EC50 26.5 nM) compared with native PYY(3-36) (EC50 16.0 nM), with the null control having an EC50 of 1.8 μM. In vivo experiments were performed in young adult male Sprague Dawley rats (9 wk). Daily treatments were delivered sc in five 1-hour pulses, each pulse delivering 5-10 nmol/kg, by implanted microinfusion pumps. Increases in hindbrain Fos expression were comparable 90 minutes after B12-PYY(3-36) or PYY3-36 injection relative to saline or B12-PYYC36. Food intake was reduced during a 5-day treatment for both B12-PYY(3-36)- (24%, P = .001) and PYY(3-36)-(13%, P = .008) treated groups relative to baseline. In addition, reduction of food intake after the three dark cycle treatment pulses was more consistent with B12-PYY(3-36) treatment (-26%, -29%, -27%) compared with the PYY(3-36) treatment (-3%, -21%, -16%), and B12-PYY(3-36) generated a significantly longer inhibition of food intake vs. PYY(3-36) treatment after the first two pulses (P = .041 and P = .036, respectively). These findings demonstrate a stronger, more consistent, and longer inhibition of food intake after the pulses of B12-PYY(3-36) conjugate compared with the native PYY(3-36).