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Query: UMLS:C0028754 (obesity)
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Accumulation of dorsocervical fat, or a "buffalo hump" (BH), is commonly reported in adults with HIV-associated lipodystrophy (HIVLD). The pathogenesis underlying this aspect of a syndrome characterized by loss of subcutaneous fat from other body sites is poorly understood. We aimed to identify risk factors for a BH in HIV-infected adults in cross-sectional analyses of 2 HIV-infected ambulatory populations. The first group (Australian Lipodystrophy Prevalence Survey [APS]) consisted of 1348 Australian HIV-infected adults (95% male) irrespective of changes in body composition. The second group (Lipodystrophy Case Definition [LDCD] study) comprised 417 subjects (83% male) with at least 1 reported moderate or severe feature of HIVLD. A BH was reported in 24 (2%) APS subjects and 79 (19%) LDCD study subjects. A BH was not an isolated finding. Patients with a BH had a high prevalence of other features of HIVLD, similar to lipodystrophic patients without a BH, such as facial lipoatrophy reported in 100% and 61% BH-positive subjects from the APS and LDCD study, respectively. In both groups, those with a BH had higher fasting insulin (P<or=0.007), a higher body mass index (P<or=0.003), a higher waist/hip ratio (P<or=0.001), higher limb fat (P<or=0.003), and higher systolic blood pressure (P<0.05). On multivariate analysis, higher serum insulin, systolic blood pressure, age, and duration of exposure to ritonavir were independently associated with a BH in the APS group. In the LDCD group, higher insulin, diastolic blood pressure, and duration of exposure to zidovudine were independently associated with a BH. There was no association between a BH and hyperlipidemia. These data show that a BH is associated with other physical features of the lipodystrophy phenotype and suggest that hyperinsulinemia, a feature common to HIVLD, obesity, and hypercortisolism, is an important component of this phenotype, thus warranting closer monitoring of BH-positive patients for glucose intolerance and diabetes.
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PMID:Buffalo hump seen in HIV-associated lipodystrophy is associated with hyperinsulinemia but not dyslipidemia. 1567

Progresses in molecular biology have highlighted the central role of adipocytes in the development of obesity and other nutrition based disorders. Adipocytes, by virtue of their excellent and sensitive molecular machinery, seem to reflect nutritional alterations very precisely. Adipocyte determination and differentiation factor 1 (ADD1)/sterol regulatory element binding protein-1c (SREBP-1c), which is the main transcription factor, regulates the characteristic features of adipocyte, senses the glucose and fat excess and draws the excess into the adipocyte to preserve energy, and maintains the blood biochemistry within physiological ranges. ADD1/SREBP-1c has regulatory functions via transactivation over the other important mature adipocyte markers such as leptin, peroxisome proliferator-activated receptor gamma (PPARgamma) and lipogenic enzymes. In this paper, considering to the role of ADD1/SREBP-1c on adipogenic markers, two new concepts have been defined: the first is sensitive adipocyte, implying a fat cell that functions perfectly at molecular level; and the second is adipocyte insensitivity syndrome (AIS), in which deviations from the optimal function of adipocyte leads to various metabolic abnormalities. The two extreme ends for adipocyte function; obesity and lipodystrophy, and intermediate spectrums between these are categorized into four subgroups. According to this categorization, responses of adipogenic markers to the stimulation of the master transcription factor, ADD1/SREBP-1c might be different in adipocytes: higher lipogenic enzymes activities in type I AIS, insufficient transactivation of leptin in type II AIS, failure in the expression of PPARgamma in type III AIS, and insufficient increases of lipogenic enzymes in type IV AIS. The novel AIS classification, which asserts that the adipocyte has a central importance for the development of metabolic devastating diseases like obesity, metabolic syndrome, type 2 diabetes and atherosclerosis, provides simpler but effective answers for the puzzle by unifying the recent, good quality studies and points out to new therapeutic approaches, highlighting the possible molecular defects.
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PMID:Adipocyte insensitivity syndromes -- novel approach to nutritional metabolic problems including obesity and obesity related disorders. 1569 4

The adipose tissue stores excess energy but also produces a series of substances including cytokines (adipocytokines) which participate in regulatory processes. The physiologic and pathophysiologic relevance of these factors has only recently been described in more detail. Defects in adiponectin as well as overproduction of free fatty acids play an important role in the development of insulin resistance typical for obesity. Rare forms of obesity or lipodystrophy can now be explained by defects in the leptin system. The contribution of adipose tissue and its cytokines to the relationship between inflammation and the metabolic syndrome is currently under investigation.
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PMID:[The adipose tissue as an endocrine organ]. 1573 43

Fatty liver is extremely common in insulin-resistant patients with either obesity or lipodystrophy and it has been proposed that hepatic steatosis be considered an additional feature of the metabolic syndrome. Although insulin resistance can promote fatty liver, excessive hepatic accumulation of fat can also promote insulin resistance and could contribute to the pathogenesis of the metabolic syndrome. We sought to create a new nonobese rat model with hypertension, hepatic steatosis, and the metabolic syndrome by transgenic overexpression of a sterol-regulatory element-binding protein (SREBP-1a) in the spontaneously hypertensive rat (SHR). SREBPs are transcription factors that activate the expression of multiple genes involved in the hepatic synthesis of cholesterol, triglycerides, and fatty acids. The new transgenic strain of SHR overexpressing a dominant-positive form of human SREBP-1a under control of the phosphoenolpyruvate carboxykinase (PEPCK) promoter exhibited marked hepatic steatosis with major biochemical features of the metabolic syndrome, including hyperglycemia, hyperinsulinemia, and hypertriglyceridemia. Both oxidative and nonoxidative skeletal muscle glucose metabolism were significantly impaired in the SHR transgenic strain and glucose tolerance deteriorated as the animals aged. The SHR transgenic strain also exhibited reduced body weight and reduced adipose tissue stores; however, the level of hypertension in the transgenic SHR was similar to that in the nontransgenic SHR control. The transgenic SHR overexpressing SREBP-1a represents a nonobese rat model of fatty liver, disordered glucose and lipid metabolism, and hypertension that may provide new opportunities for studying the pathogenesis and treatment of the metabolic syndrome associated with hepatic steatosis.
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PMID:A new transgenic rat model of hepatic steatosis and the metabolic syndrome. 1580 59

Nutrition assessment is a vital component of the general care of HIV-infected adults. With access to highly active antiretroviral therapy (HAART), HIV infection may become a chronic, manageable disease. Nutritional and metabolic complications traditionally associated with HIV infection such as hypertriglyceridemia, low levels of high-density lipoprotein (HDL) cholesterol, and weight loss continue to occur. However, emerging abnormalities such as regional alterations in body shape (fat re-distribution syndrome or HIV-associated lipodystrophy), increasing body weight, high levels of low-density lipoprotein (LDL) cholesterol, insulin resistance, and other metabolic derangements may also be present. In addition, as patients are living longer, they may be susceptible to other age-related diseases such as diabetes, cardiovascular disease, and obesity. In this article, we review strategies for nutrition assessment and management in HIV-infected adults. Attention is focused on specific symptoms such as weight loss and diarrhea and specific disorders such as lipodystrophy, micronutrient deficiencies, and dyslipidemia, which commonly affect HIV-infected individuals. Proper attention to nutritional status may help to reduce the burden of disease and promote an enhanced quality of life in HIV-infected individuals.
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PMID:Nutrition assessment in HIV infection. 1585 Feb 29

The metabolic syndrome (MetS) is a common phenotype that is clinically defined by threshold values applied to measures of central obesity, dysglycemia, dyslipidemia, and/or elevated blood pressure, which must be present concurrently in any one of a variety of combinations. Insulin resistance, although not a defining component of the MetS, is nonetheless considered to be a core feature. MetS is important because it is rapidly growing in prevalence and is strongly related to the development of cardiovascular disease. To define etiology, pathogenesis and expression of MetS, we have studied patients, specifically Canadian families and communities. One example is familial partial lipodystrophy (FPLD), a rare monogenic form of insulin resistance caused by mutations in either LMNA, encoding nuclear lamin A/C (subtype FPLD2), or in PPARG, encoding peroxisomal proliferator-activated receptor-gamma (subtype FPLD3). Because it evolves slowly and recapitulates key clinical and biochemical attributes, FPLD seems to be a useful monogenic model of MetS. A second example is the disparate MetS prevalence between two Canadian aboriginal groups that is mirrored by disparate prevalence of diabetes and cardiovascular disease. Careful phenotypic evaluation of such special cases of human MetS by using a wide range of diagnostic methods, an approach called "phenomics," may help uncover early presymptomatic disease biomarkers, which in turn might reveal new pathways and targets for interventions for MetS, diabetes, and atherosclerosis.
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PMID:Genetic and physiological insights into the metabolic syndrome. 1589 Jul 90

Obesity is not necessary to observe insulin resistance in humans since severe insulin resistance also characterizes patients lacking subcutaneous fat such as those with HAART (highly-active antiretroviral therapy) - associated lipodystrophy. Both the obese and the lipodystrophic patients have, however, an increase in the amount of fat hidden in the liver. Liver fat content can be non-invasively accurately quantified by proton magnetic resonance spectroscopy. It is closely correlated with fasting insulin and direct measures of hepatic insulin sensitivity while the amount of subcutaneous adipose tissue is not. The causes of interindividual variation in liver fat content independent of obesity are largely unknown but could involve differences in signals from adipose tissue such as in the amount of adiponectin produced and differences in fat intake. Adiponectin deficiency characterizes both lipodystrophic and obese insulin resistant individuals, and serum levels correlate with liver fat content. Liver fat content can be decreased by weight loss. In addition, treatment of both lipodystrophic and type 2 diabetic patients with PPARgamma agonists but not metformin decreases liver fat and increases adiponectin levels. Markers of liver fat such as serum alanine aminotransferase activity have been shown to predict type 2 diabetes in several studies independent of obesity. The fatty liver thus may help to explain why some but not all obese individuals are insulin resistant and why even lean individuals may be insulin resistant, and thereby at risk of developing type 2 diabetes and cardiovascular disease.
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PMID:The fatty liver and insulin resistance. 1589 48

Childhood NAFLD has become an important childhood liver disease, and it is probably highly prevalent. The full of spectrum of NAFLD has been identified in children. It is not currently known whether or not simple hepatic steatosis in children is benign or whether it evolves to NASH over time. In contrast, childhood NASH certainly can have serious consequences. Cirrhosis is apparently rare in children with NAFLD, but it definitely occurs. Childhood NAFLD may occur in very young children, and there is no female predominance in the pediatric age bracket. Children present with vague abdominal pain, if they have any symptoms at all, but frequently hepatic steatosis is found incidentally on abdominal imaging. Laboratory studies show that serum aminotransferase abnormalities are rather moderate, with serum alanine aminotransferase (ALT) more elevated than serum aspartate aminotransferase (AST). Hypertriglyceridemia is the typical blood lipid abnormality, although hypercholesterolemia may occur. NASH may be more severe in children from certain ethnic groups, including Hispanics and Asians, or in association with certain metabolic disorders characterized by abnormalities in insulin receptor structure or signaling, such as lipodystrophy syndromes. Weight loss through dietary redesign and a regimen of regular exercise remains the mainstay for treatment for childhood NAFLD. A dietary strategy to minimize postprandial hyperinsulinemia and overall fat intake, such as a low glycemic index diet, may be the best dietary strategy. The real efficacy of drug treatments in children requires further investigation. The overriding message is that childhood obesity poses important health problems, including but not limited to potentially severe chronic liver disease. Early diagnosis of children who are only overweight is a worthy goal so that strategies to limit obesity can be instituted as early as possible. Identification of genetic risks is important, but management will invariably require changes in environmental factors. In addition to individual treatment, a multifaceted, societal initiative is required for solving the childhood obesity epidemic.
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PMID:Non-alcoholic fatty liver disease (NAFLD) in children. 1597 Apr 96

Ectopic fat accumulation has been implicated as a contributing factor in the abnormal metabolic state of obesity. One human model of ectopic fat deposition is generalized lipodystrophy. Generalized lipodystrophy is a rare disorder characterized by a profound deficiency of adipose tissue with resultant loss of triglyceride storage capacity and reduced adipokines, including leptin. Subjects with generalized lipodystrophy and reduced leptin levels often have an increased appetite leading to hyperphagia. Excess fuel consumption, coupled with a lack of adipose tissue, contributes to the significant ectopic triglyceride accumulation in the muscle and liver seen in these subjects. This ectopic fat, along with the deficiency in leptin signaling and perhaps other adipokines, likely contributes to insulin resistance, diabetes, and hepatic steatosis. We report here the long-term effects of leptin replacement in a cohort of these subjects. Fifteen patients with generalized lipodystrophy were treated with twice-daily recombinant methionyl human leptin (r-metHuLeptin) for 12 months. We evaluated metabolic parameters at baseline and every 4 months. Antidiabetes medications were decreased or discontinued as necessary. Reductions were seen in serum fasting glucose (from 205 +/- 19 to 126 +/- 11 mg/dl; P < 0.001), HbA1c (from 9 +/- 0.4 to 7.1 +/- 0.5%; P < 0.001), triglycerides (from 1,380 +/- 500 to 516 +/- 236 mg/dl; P < 0.001), LDL (from 139 +/- 16 to 85 +/- 7 mg/dl; P < 0.01), and total cholesterol (from 284 +/- 40 to 167 +/- 21 mg/dl; P < 0.01). HDL was unchanged (from 31 +/- 3 to 29 +/- 2 mg/dl; P = 0.9). Liver volumes were significantly reduced (from 3,663 +/- 326 to 2,190 +/- 159 cm3; P < 0.001), representing loss of steatosis. Decreases were seen in total body weight (from 61.8 +/- 3.6 to 57.4 +/- 3.4 kg; P = 0.02) and resting energy expenditure (from 1,929 +/- 86 to 1,611 +/- 101 kcal/24 h; P < 0.001). R-metHuLeptin led to significant and sustained improvements in glycemia, dyslipidemia, and hepatic steatosis. Leptin represents the first novel, effective, long-term treatment for severe forms of lipodystrophy.
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PMID:Long-term efficacy of leptin replacement in patients with generalized lipodystrophy. 1598 99

Lipodystrophy and obesity represent extreme and opposite ends of the adiposity spectrum and have typically been attributed to alterations in the expression or function of distinct sets of genes. We previously demonstrated that lipin deficiency impairs adipocyte differentiation and causes lipodystrophy in the mouse. Using two different tissue-specific lipin transgenic mouse strains, we now demonstrate that enhanced lipin expression in either adipose tissue or skeletal muscle promotes obesity. This occurs through diverse mechanisms in the two tissues, with lipin levels in adipose tissue influencing the fat storage capacity of the adipocyte, and lipin levels in skeletal muscle acting as a determinant of whole-body energy expenditure and fat utilization. Thus, variations in lipin levels alone are sufficient to induce extreme states of adiposity and may represent a mechanism by which adipose tissue and skeletal muscle modulate fat mass and energy balance.
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PMID:Lipin, a lipodystrophy and obesity gene. 1605 38


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