Elaine Cochran

Postreceptor insulin resistance contributes to human dyslipidemia and hepatic steatosis.

Metabolic dyslipidemia is characterized by high circulating triglyceride (TG) and low HDL cholesterol levels and is frequently accompanied by hepatic steatosis. Increased hepatic lipogenesis contributes to both of these problems. Because insulin fails to suppress gluconeogenesis but continues to stimulate lipogenesis in both obese and lipodystrophic insulin-resistant mice, it has been proposed that a selective postreceptor defect in hepatic insulin action is central to the pathogenesis of fatty liver and hypertriglyceridemia in these mice. Here we show that humans with generalized insulin resistance caused by either mutations in the insulin receptor gene or inhibitory antibodies specific for the insulin receptor uniformly exhibited low serum TG and normal HDL cholesterol levels. This was due at least in part to surprisingly low rates of de novo lipogenesis and was associated with low liver fat content and the production of TG-depleted VLDL cholesterol particles. In contrast, humans with a selective postreceptor defect in AKT2 manifest increased lipogenesis, elevated liver fat content, TG-enriched VLDL, hypertriglyceridemia, and low HDL cholesterol levels. People with lipodystrophy, a disorder characterized by particularly severe insulin resistance and dyslipidemia, demonstrated similar abnormalities. Collectively these data from humans with molecularly characterized forms of insulin resistance suggest that partial postreceptor hepatic insulin resistance is a key element in the development of metabolic dyslipidemia and hepatic steatosis.

Leptin reverses nonalcoholic steatohepatitis in patients with severe lipodystrophy.

Severe lipodystrophy is characterized by diminished adipose tissue and hypoleptinemia, leading to ectopic triglyceride accumulation. In the liver, this is associated with steatosis, potentially leading to nonalcoholic steatohepatitis (NASH). We investigated the prevalence of NASH and the effect of leptin replacement in these patients. Ten patients with either generalized lipodystrophy (8 patients) or Dunnigans partial lipodystrophy (2 patients) were included in this analysis. Paired liver biopsy specimens were obtained at baseline and after treatment with recombinant methionyl human leptin (r‐metHuLeptin), mean duration 6.6 months. The extents of portal and parenchymal inflammation, steatosis, ballooning, presence of Mallory bodies, and fibrosis in liver biopsy specimens were scored using a previously validated system developed to assess NASH activity. Histological disease activity was defined as the sum of ballooning, steatosis, and parenchymal inflammation scores. We concurrently tested serum triglycerides and aminotransferases and estimations of liver volume and fat content by magnetic resonance imaging. Eight of 10 patients met histological criteria for NASH at baseline. After treatment with r‐metHuLeptin, repeat histological examinations showed significant improvements in steatosis (P = .006) and ballooning injury (P = .005), with a reduction of mean NASH activity by 60% (P = .002). Fibrosis was unchanged. Significant reductions were seen in mean serum triglycerides (1206→226 mg/dL, P = .002), glucose (220→144 mg/dL, P = .02), insulin (46.4→24.8 μIU/mL, P = .004), ALT (54→24 U/L, P = .02), AST (47→22 U/L, P = .046), liver volume (3209→2391 cm3, P = .007), and liver fat content (31→11%, P = .006). In conclusion, r‐metHuLeptin therapy significantly reduced triglycerides, transaminases, hepatomegaly, and liver fat content. These reductions were associated with significant reductions in steatosis and the hepatocellular ballooning injury seen in NASH. (HEPATOLOGY 2005;41:753–760.)

Clinical course of genetic diseases of the insulin receptor (type A and Rabson-Mendenhall syndromes): A 30-year prospective

Abstract: The interaction of insulin with its cell surface receptor is the first step in insulin action and the first identified target of insulin resistance. The insulin resistance in several syndromic forms of extreme insulin resistance has been shown to be caused by mutations in the receptor gene. We studied 8 female patients with the type A form of extreme insulin resistance and 3 patients (2 male and 1 female) with the Rabson-Mendenhall syndrome and followed the natural history of these patients for up to 30 years. The 11 patients ranged in age from 7 to 32 years at presentation. All 11 patients had extreme insulin resistance, acanthosis nigricans, and hyperandrogenism in the female patients, and all but 1 were of normal body weight. This phenotype strongly predicts mutations in the insulin receptor: of the 8 patients studied, 7 were found to have mutations. Similar results from the literature are found in other patients with type A and Rabson-Mendenhall syndromes and leprechaunism. The hyperandrogenic state resulting from hyperinsulinemia and insulin resistance in these patients was extreme: 6 of 8 patients had ovarian surgery to correct the polycystic ovarian syndrome and elevation of serum testosterone. By contrast, a larger group of insulin-resistant patients who were obese with hyperandrogenism, insulin resistance, and acanthosis nigricans (HAIR-AN syndrome) did not have a high probability of mutations in the insulin receptor. The morbidity and mortality of these patients were high: 3 of 11 died, 9 of 11 were diabetic and 1 had impaired glucose tolerance, and 7 of 9 patients had 1 or more severe complication of diabetes. Our literature review revealed that the mortality of leprechaunism is so high that the term leprechaunism should be restricted to infants or young children under 2 years of age. Analogous to patients with the common forms of type 2 diabetes, these patients had a heterogeneous course. In 2 patients who were able to maintain extremely high endogenous insulin production, the fasting blood glucose remained normal even though post-glucose-challenge levels were elevated. Most patients, however, required large doses of exogenous insulin to ameliorate the severe hyperglycemia. Preliminary results of a recent study suggest that recombinant leptin administration may benefit these patients with severe insulin resistance.

Genetic Syndromes of Severe Insulin Resistance

Insulin resistance is among the most prevalent endocrine derangements in the world, and it is closely associated with major diseases of global reach including diabetes mellitus, atherosclerosis, nonalcoholic fatty liver disease, and ovulatory dysfunction. It is most commonly found in those with obesity but may also occur in an unusually severe form in rare patients with monogenic defects. Such patients may loosely be grouped into those with primary disorders of insulin signaling and those with defects in adipose tissue development or function (lipodystrophy). The severe insulin resistance of both subgroups puts patients at risk of accelerated complications and poses severe challenges in clinical management. However, the clinical disorders produced by different genetic defects are often biochemically and clinically distinct and are associated with distinct risks of complications. This means that optimal management of affected patients should take into account the specific natural history of each condition. In clinical practice, they are often underdiagnosed, however, with low rates of identification of the underlying genetic defect, a problem compounded by confusing and overlapping nomenclature and classification. We now review recent developments in understanding of genetic forms of severe insulin resistance and/or lipodystrophy and suggest a revised classification based on growing knowledge of the underlying pathophysiology.

Autoimmune forms of hypoglycemia.

Autoimmune syndromes are a rare cause of hypoglycemia characterized by elevated levels of insulin in the presence of either anti-insulin antibodies (insulin autoimmune syndrome) or anti-insulin receptor antibodies (type B insulin resistance). Insulin autoimmune syndrome is the third leading cause of hypoglycemia in Japan, but has rarely been described in the non-Asian population. In the current study, we report the clinical and biochemical characteristics and clinical course of 2 white patients with insulin autoimmune syndrome, and present a literature review of non-Asian patients reported with insulin autoimmune syndrome. Also, we describe the clinical and biochemical characteristics of patients reported in the literature with type B insulin resistance who manifested hypoglycemia. We compare the clinical and laboratory features of insulin autoimmune syndrome and type B insulin resistance with each other and with other forms of hyperinsulinemic hypoglycemia. Autoimmune forms of hypoglycemia are uncommon. However, they should be considered in any patient with hypoglycemia in the setting of unsuppressed insulin levels associated with anti-insulin or anti-insulin receptor antibodies. Making the correct diagnosis may spare a hypoglycemic patient from an unnecessary pancreatic surgical procedure. Abbreviations: BMI = body mass index, CRC = Clinical Research Center, HLA = human leukocyte antigen, NIH = National Institutes of Health, SLE = systemic lupus erythematosus.

Paradoxical Elevation of High–Molecular Weight Adiponectin in Acquired Extreme Insulin Resistance Due to Insulin Receptor Antibodies

Total plasma adiponectin and high–molecular weight (HMW) polymeric adiponectin are strongly positively correlated with insulin sensitivity. However, we have recently reported paradoxical hyperadiponectinemia in patients with severe insulin resistance due to genetically defective insulin receptors. This implies either that the insulin receptor has a critical physiological role in controlling adiponectin production and/or clearance or that constitutive insulin receptor dysfunction influences adiponectin levels through developmental effects. The aim of the current study was to distinguish between these possibilities using a human model of reversible antibody-mediated insulin receptor dysfunction and to refine the previous observations by determining adiponectin complex distribution. Cross-sectional and longitudinal determination of fasting plasma adiponectin and adiponectin complex distribution was undertaken in patients with extreme insulin resistance due to insulin receptor mutations, anti-insulin receptor antibodies (type B insulin resistance), or an undefined cause. Despite extreme insulin resistance, patients with type B insulin resistance (all women; mean age 42 years [range 12–54]) had dramatically elevated total plasma adiponectin compared with the general population (mean 43.0 mg/l [range 31.3–54.2] vs. 8.9 mg/l [1.5–28.5 for BMI <25 kg/m2]), which was accounted for largely by HMW polymers. Hyperadiponectinemia resolved in parallel with reduction of insulin receptor antibodies and clinical resolution of insulin resistance. Although the well-established inverse relationship between plasma insulin and adiponectin levels may, in part, reflect positive effects of adiponectin on insulin sensitivity, these data suggest that the magnitude of the effect of insulin action on adiponectin levels may have been underestimated.

Predictors of acquired lipodystrophy in juvenile-onset dermatomyositis and a gradient of severity

We describe the clinical features of 28 patients with juvenile dermatomyositis (JDM) and 1 patient with adult-onset dermatomyositis (DM), all of whom developed lipodystrophy (LD) that could be categorized into 1 of 3 phenotypes, generalized, partial, or focal, based on the pattern of fat loss distribution. LD onset was often delayed, beginning a median of 4.6 years after diagnosis of DM. Calcinosis, muscle atrophy, joint contractures, and facial rash were DM disease features found to be associated with LD. Panniculitis was associated with focal lipoatrophy while the anti-p155 autoantibody, a newly described myositis-associated autoantibody, was more associated with generalized LD. Specific LD features such as acanthosis nigricans, hirsutism, fat redistribution, and steatosis/nonalcoholic steatohepatitis were frequent in patients with LD, in a gradient of frequency and severity among the 3 sub-phenotypes. Metabolic studies frequently revealed insulin resistance and hypertriglyceridemia in patients with generalized and partial LD. Regional fat loss from the thighs, with relative sparing of fat loss from the medial thighs, was more frequent in generalized than in partial LD and absent from DM patients without LD. Cytokine polymorphisms, the C3 nephritic factor, insulin receptor antibodies, and lamin mutations did not appear to play a pathogenic role in the development of LD in our patients. LD is an under-recognized sequela of JDM, and certain DM patients with a severe, prolonged clinical course and a high frequency of calcinosis appear to be at greater risk for the development of this complication. High-risk JDM patients should be screened for metabolic abnormalities, which are common in generalized and partial LD and result in much of the LD-associated morbidity. Further study is warranted to investigate the pathogenesis of acquired LD in patients with DM. Abbreviations: CI = confidence interval, CT = computerized tomography, dlk = delta-like, DM= dermatomyositis, DXA = dual-energy X-ray absorptiometry, HDL = high-density lipoprotein, HIV = human immunodeficiency virus, HOMA-IR = homeostasis model assessment of insulin resistance, IL = interleukin, IR = insulin resistance, JDM = juvenile dermatomyositis, LA = lipoatrophy, LD = lipodystrophy, LDL = low-density lipoprotein, LMNA= lamin A, MRI = magnetic resonance imaging, NASH = nonalcoholic steatohepatitis, NIH = National Institutes of Health, OGTT = oral glucose tolerance test, OR = odds ratio, PCR = polymerase chain reaction, TNF = tumor necrosis factor, TTP = tristetraprolin.

The liver diseases of lipodystrophy: The long-term effect of leptin treatment

BACKGROUND & AIMS Lipodystrophies are hypoleptinemic conditions characterized by fat loss, severe insulin resistance, hypertriglyceridemia, and ectopic fat accumulation. Non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) are also features of this condition. We studied the spectrum of liver disease in lipodystrophy and the effects of leptin replacement. METHODS This was an open-label, prospective study of leptin therapy in patients with inherited and acquired lipodystrophy at the National Institutes of Health. Liver biopsies were performed at baseline (N=50) and after leptin replacement (N=27). NASH activity was assessed using the NASH Clinical Research Network (CRN) scoring system. Fasting blood glucose, triglyceride, hemoglobin A1c and liver enzymes were measured at baseline and at the time of the final liver biopsy. RESULTS In leptin-treated patients, 86% met criteria for NASH at baseline, while only 33% had NASH after leptin replacement for 25.8 ± 3.7 months (mean ± SE, p=0.0003). There were significant improvements in steatosis grade (reduction of mean score from 1.8 to 0.9) and ballooning injury scores (from 1.2 to 0.4), with a 44.2% reduction in mean NAFLD activity score (p<0.0001). Patients who already had fibrosis remained stable on leptin replacement. We observed significant improvement in metabolic profile, ALT and AST. In addition to NASH, four patients with acquired generalized lipodystrophy (AGL) had autoimmune hepatitis. CONCLUSIONS The fundamental liver disease of lipodystrophy is NASH, although autoimmune hepatitis was observed in some patients with AGL. Leptin appears to be a highly effective therapy for NASH in hypoleptinemic lipodystrophic patients.

Clinical effects of long-term metreleptin treatment in patients with lipodystrophy.

OBJECTIVE To evaluate the long-term clinical effect of treatment with metreleptin (an analogue of human leptin) on glycemic and lipid abnormalities and markers of hepatic steatosis in patients with inherited or acquired lipodystrophy. METHODS Fifty-five patients (36 with generalized lipodystrophy and 19 with partial lipodystrophy) with at least 1 of 3 metabolic abnormalities (diabetes mellitus, fasting triglyceride level ≥200 mg/dL, and insulin resistance) and low leptin levels received subcutaneous injections of metreleptin once or twice daily in an ongoing clinical trial at the National Institutes of Health. RESULTS At baseline, hemoglobin A1c-8.5% ± 2.1% (mean ± standard deviation [SD])-and triglycerides-479 ± 80 mg/dL (geometric mean ± standard error [SE])-were substantially elevated. Robust and sustained reductions in both variables were evident for the observed patient population during a 3-year metreleptin treatment period (-2.1% ± 0.5% [mean ± SE] and -35.4% ± 13.7% [mean ± SE], respectively). Mean alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were elevated at baseline (100 ± 120 U/L and 71 ± 77 U/L [mean ± SD], respectively) and decreased by -45 ± 19 U/L and -33 ± 14 U/L (mean ± SE), respectively, during the 3-year metreleptin treatment period. Improvements in hemoglobin A1c, triglycerides, ALT, and AST were more pronounced in the subsets of patients having elevated levels at baseline. The most notable adverse events observed in this patient population were likely attributable to underlying metabolic abnormalities or comorbidities. CONCLUSION Metreleptin treatment substantially reduced glycemic variables, triglycerides, and liver enzymes (ALT and AST) and demonstrated durability of response throughout a 3-year treatment period. These results support metreleptin as a potential treatment for certain metabolic disorders (for example, diabetes mellitus and hypertriglyceridemia) associated with lipodystrophy.

Plasma adiponectin as a marker of insulin receptor dysfunction: clinical utility in severe insulin resistance.

OBJECTIVE—Severe insulin resistance is associated with high morbidity. Identification of severely insulin-resistant patients who have genetic or acquired insulin receptor dysfunction may aid therapeutic decision making; however, onerous diagnostic tests allied to a low frequency of insulin receptor dysfunction often preclude formal diagnosis. Our previous observation of paradoxical hyperadiponectinemia in insulin receptoropathy provides a possible basis for a simpler and cheaper screening test. RESEARCH DESIGN AND METHODS—Receiver operating characteristics analysis was used to determine diagnostic thresholds for insulin receptoropathy in severe insulin resistance for adiponectin and for the insulin-regulated hepatic proteins sex hormone–binding globulin (SHBG) and IGF binding protein-1 (IGFBP-1). RESULTS—Adiponectin >7 mg/l in severe insulin resistance had a 97% positive predictive value for insulin receptoropathy and <5 mg/l a 97% negative predictive value. IGFBP-1 and SHBG had lesser, though still significant, utility. CONCLUSIONS—Use of these markers is likely to have significant value in accelerating the diagnosis of insulin receptoropathies.