Long-term octreotide treatment reduced hyperinsulinemia, excess body weight and skin lesions in severe obesity with acanthosis nigricans

Acanthosis nigricans: A review

BACKGROUND

Acanthosis nigricans (AN) is a cutaneous disorder characterized by symmetric velvety hyperpigmented plaques on intertriginous areas like axilla, neck, inframammary, and groin.

AIMS

To summarize the pathophysiology and classification of AN, provide an update of diagnostic testing strategies, and describe the current therapeutic options described so far in the literature for this disease.

METHODS

A comprehensive english language literature search across multiple databases (PubMed, EMBASE, MEDLINE, and Cochrane) for keywords (alone and in combination) was performed. MeSH as well as non-MeSH terms such as "acanthosis nigricans," "classification," "pathophysiology," "diagnosis," "treatment," "topical drugs," "systemic drugs," "chemical peeling," and "lasers" were taken into consideration.

RESULTS

The pathophysiology of AN revolves around a multifactorial stimulation of proliferation of epidermal keratinocytes and dermal fibroblasts. Various types of AN include benign, obesity-associated, syndromic, malignant, acral, unilateral, medication-induced, and mixed-type. Homeostasis model assessment-insulin resistance (HOMA-IR) is a good tool for assessment of insulin resistance. Management involves general measures (weight reduction and addressing the underlying cause, if any), topical drugs (retinoids, vitamin D analogs, and keratolytics), oral drugs (retinoids and insulin sensitizers), chemical peels (trichloroacetic acid), and lasers (Long pulsed alexandrite, fractional 1550-nm erbium fiber, and CO₂ ).

CONCLUSION

Acanthosis nigricans is a treatable condition; however, complete cure and disappearance of lesions are difficult to achieve. Weight reduction is the most scientific and practical management strategy. Long-term studies and further research is warranted in the pathophysiology and treatment of this common condition.

Current treatment options for acanthosis nigricans

Acanthosis nigricans (AN) is a common dermatologic manifestation of systemic disease that is associated with insulin resistance, diabetes mellitus, obesity, internal malignancy, endocrine disorders, and drug reactions. Treatment of AN primarily focuses on resolution of the underlying disease processes causing the velvety, hyperpigmented, hyperkeratotic plaques found on the skin. While the goal of therapy is to treat the primary cause, cosmetic resolution of AN lesions can be important for patients and their quality of life. Treatment options for AN have not been extensively studied; however, smaller powered clinical trials and case reports exist in the literature. Our review aims to explore and evaluate the current treatment options that exist for AN.

A causal role for hyperinsulinemia in obesity

Insulin modulates the biochemical pathways controlling lipid uptake, lipolysis and lipogenesis at multiple levels. Elevated insulin levels are associated with obesity, and conversely, dietary and pharmacological manipulations that reduce insulin have occasionally been reported to cause weight loss. However, the causal role of insulin hypersecretion in the development of mammalian obesity remained controversial in the absence of direct loss-of-function experiments. Here, we discuss theoretical considerations around the causal role of excess insulin for obesity, as well as recent studies employing mice that are genetically incapable of the rapid and sustained hyperinsulinemia that normally accompanies a high-fat diet. We also discuss new evidence demonstrating that modest reductions in circulating insulin prevent weight gain, with sustained effects that can persist after insulin levels normalize. Importantly, evidence from long-term studies reveals that a modest reduction in circulating insulin is not associated with impaired glucose homeostasis, meaning that body weight and lipid homeostasis are actually more sensitive to small changes in circulating insulin than glucose homeostasis in these models. Collectively, the evidence from new studies on genetic loss-of-function models forces a re-evaluation of current paradigms related to obesity, insulin resistance and diabetes. The potential for translation of these findings to humans is briefly discussed.

Acanthosis nigricans: A fold (intertriginous) dermatosis

Acanthosis nigricans (AN) is a mucocutaneous disorder that is characterized by focal or diffuse hyperkeratotic, surfaces, which are symmetrically distributed hyperpigmented lesions of the skin. It rarely affects mucosal surfaces like oral cavities. Although it is commonly seen in adolescents, AN is also increasingly seen in children who are obese. Recent studies have found that AN can be a cutaneous indicator of insulin resistance and malignancy. Acanthosis nigricans has been associated with type 2 diabetes mellitus, obesity, endocrinopathies, drugs, and malignancies.

Dermatologic manifestation of diabetes

With the rising incidence of diabetes mellitus (DM) in the US, it is of paramount importance that practitioners understand the complications of DM and how best to manage them. Diabetes affects every organ system and the skin is no exception. There are numerous cutaneous manifestations of DM that have similar etiologies and result from the same pathologic mechanisms as the internal complications of this disease state. In addition, skin manifestations may precede the diagnosis of diabetes. The present article reviews both the common and less common cutaneous manifestations of DM, including presenting lesions, pathogenesis, and management.

Treatment options in insulin resistance obesity-related acanthosis nigricans

OBJECTIVE

To evaluate the literature to determine which oral and topical medications are most effective in the treatment of insulin resistance obesity-related acanthosis nigricans (IRORAN).

DATA SOURCES

A MEDLINE literature search was conducted (1950-January 2008) using the search terms acanthosis nigricans (AN), metformin, rosiglitazone, octreotide, retinoic acid, acitretin, etretinate, and isotretinoin. The search was limited to articles on treatment of IRORAN in humans written in the English language. Articles were retrieved and all references were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Articles selected for inclusion were limited to AN related to obesity with no other underlying etiology. Clinical trials and case reports using monotherapy were included.

DATA SYNTHESIS

Metformin, rosiglitazone, octreotide, vitamin D analogs, and retinoic acid have been used in the treatment of IRORAN. In one randomized trial, metformin 500 mg 3 times daily was compared with rosiglitazone 4 mg once daily. Neither treatment demonstrated significant improvements in AN; however, rosiglitazone did significantly decrease serum insulin levels. In a second clinical trial and in several case reports, AN and hyperinsulinemia did show improvement with metformin treatment. After a 6-month period, octreotide improved IRORAN, body weight, and glucose/insulin response to a meal. The improvements persisted for 6 additional months after discontinuation of octreotide. Vitamin D analogs and retinoids produced inconsistent results in 5 separate case reports.

CONCLUSIONS

IRORAN is a growing problem, particularly in children and adolescents, secondary to the increase in the prevalence of obesity. Treatment of IRONAN should focus on reversal of the underlying hyperinsulinemia. Patients with IRORAN may benefit from a trial of metformin for improvement of lesions and underlying hyperinsulinemia.

Obesity and the skin: Skin physiology and skin manifestations of obesity

Obesity is widely recognized as an epidemic in the Western world; however, the impact of obesity on the skin has received minimal attention. The purpose of this article is to highlight the association between obesity and dermatologic conditions. We review the impact of obesity on the skin, including skin physiology, skin manifestations of obesity, and dermatologic diseases aggravated by obesity. Obesity is responsible for changes in skin barrier function, sebaceous glands and sebum production, sweat glands, lymphatics, collagen structure and function, wound healing, microcirculation and macrocirculation, and subcutaneous fat. Moreover, obesity is implicated in a wide spectrum of dermatologic diseases, including acanthosis nigricans, acrochordons, keratosis pilaris, hyperandrogenism and hirsutism, striae distensae, adiposis dolorosa, and fat redistribution, lymphedema, chronic venous insufficiency, plantar hyperkeratosis, cellulitis, skin infections, hidradenitis suppurativa, psoriasis, insulin resistance syndrome, and tophaceous gout. We review the clinical features, evidence for association with obesity, and management of these various dermatoses and highlight the profound impact of obesity in clinical dermatology.

LEARNING OBJECTIVE

After completing this learning activity, participants should be aware of obesity-associated changes in skin physiology, skin manifestations of obesity, and dermatologic diseases aggravated by obesity, and be able to formulate a pathophysiology-based treatment strategy for obesity-associated dermatoses.

Dermatologic manifestations of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) affects 5-10% of reproductive-aged women and is one of the most common endocrine disorders in women. The disorder is commonly characterized by elevated levels of androgen and insulin. Women with PCOS may present with a range of signs and symptoms, and face increased risks of reproductive, metabolic, cardiovascular, psychologic, and neoplastic sequelae, particularly if the condition is left unrecognized or untreated. The clinical definition of PCOS has changed in recent years and includes as one of its cardinal criteria the dermatologic manifestations of hyperandrogenism, chiefly hirsutism, acne vulgaris, and androgenetic alopecia. Acanthosis nigricans, a cutaneous sign of hyperinsulinemia, may also be present. These dermatologic features may provide early clinical clues to recognition of PCOS, and treatment of these cutaneous conditions may improve the patient's quality of life and psychologic well-being. The effects of androgen on pilosebaceous units in the skin can vary by anatomic location, producing pathophysiologic effects on hair growth and differentiation, sebaceous gland size and activity, and follicular keratinization. Treatment modalities may include hormonal therapy intended to modulate androgen production and action as well as non-hormonal therapies directed toward specific dermatologic conditions.

Acanthosis nigricans associated with insulin resistance : pathophysiology and management

The association of acanthosis nigricans, skin tags, diabetes mellitus due to insulin resistance, and obesity in adolescents and young adults represents a well defined syndrome. Hyperandrogenism may also be present. The endocrine origin of this condition is beyond doubt. Insulin and insulin-like growth factor-1, and their receptors on keratinocytes are obviously involved in the complex regulations leading to the peculiar epidermal hyperplasia. This condition is unrelated to other types of acanthosis nigricans, including the congenital and the paraneoplastic types. Control of obesity contributes largely to reverse the whole process, essentially by reducing both insulin resistance and compensatory hyperinsulinemia. Several drugs including metformin, octreotide, retinoids and topical colecalciferol (vitamin D(3)) analogs are also beneficial in clearing acanthosis nigricans.

Obesity and dermatology

Obesity is associated with a number of dermatoses. It affects cutaneous sensation, temperature regulation, foot shape, and vasculature. Acanthosis nigricans is the most common dermatological manifestation of obesity. Skin tags are more commonly associated with diabetes than with obesity. Obesity increases the incidence of cutaneous infections that include: candidiasis, intertigo, candida folliculitis, furunculosis, erythrasma, tinea cruris, and folliculitis. Less common infections include cellulitis, necrotizing fasciitis, and gas gangrene. Leg ulcerations, lymphedema, plantar hyperkeratosis, and striae are more common with obesity. Hormonal abnormalities and genetic syndromes (Prader-Willi) are related to obesity and its dermatoses; however, cellulite is not related to obesity.

Race affects insulin and GLP-1 secretion and response to a long-acting somatostatin analogue in obese adults

OBJECTIVE

This study investigated (1) the effect of octreotide-LAR (Sandostatin-LAR Depot; Novartis) on the enteroinsular axis in a biracial cohort of severely obese adults, (2) whether octreotide suppression of insulin secretion occurs by both a direct beta-cell effect and through mediating a glucagon-like peptide 1 (GLP-1) response, and (3) whether differences in GLP-1 concentrations could explain racial differences in insulin concentrations.

DESIGN

Prospective, open-label trial using a pre-post test design.

SETTING

Single university, clinical research center.

SUBJECTS

In all, 42 healthy, severely obese Caucasian and African-American (AA) adults (93% female, 64% Caucasian, age=37.8+/-1.2 y, weight=123+/-4.2 kg, BMI=44.5+/-1 kg/m(2)), recruited through physician referral and newspaper ads, participated in the study.

INTERVENTIONS

Indices of beta-cell activity, insulin and GLP-1 response before and during a 75-gm oral glucose tolerance test were determined before and after 24 weeks of octreotide-LAR.

RESULTS

AA exhibited higher beta-cell activity, and insulin and GLP-1 concentrations than Caucasians. Octreotide-LAR suppressed the insulin and GLP-1 levels in both groups.

Suppression of insulin secretion is associated with weight loss and altered macronutrient intake and preference in a subset of obese adults

PURPOSE

Hyperinsulinemia is a common feature of many obesity syndromes. We investigated whether suppression of insulin secretion, without dietary or exercise intervention, could promote weight loss and alter food intake and preference in obese adults.

METHODS

Suppression of insulin secretion was achieved using octreotide-LAR 40 mg IM q28d for 24 weeks in 44 severely obese adults (89% female, 39% minority). Oral glucose tolerance testing was performed before and after treatment, indices of beta-cell activity (CIRgp), insulin sensitivity (CISI), and clearance (CP/I AUC) were computed, and leptin levels, 3-day food records and carbohydrate-craving measurements were obtained. DEXA evaluations were performed pre- and post-therapy in an evaluable subgroup.

RESULTS

For the entire cohort, significant insulin suppression was achieved with simultaneous improvements in insulin sensitivity, weight loss, and body mass index (BMI). Leptin, fat mass, total caloric intake, and carbohydrate craving significantly decreased. When grouped by BMI response, high responders (HR; DeltaBMI<-3 kg/m(2)) and low responders (LR; DeltaBMI between -3 and -0.5) exhibited higher suppression of CIRgp and IAUC than nonresponders (NR; DeltaBMI-0.5). CISI improved and significant declines in leptin and fat mass occurred only in HR and LR. Conversely, both leptin and fat mass increased in NR. Carbohydrate intake was markedly suppressed in HR only, while carbohydrate-craving scores decreased in HR and LR. For the entire cohort, DeltaBMI correlated with DeltaCISI, Deltafat mass, and Deltaleptin. DeltaFat mass also correlated with DeltaIAUC and DeltaCISI.

CONCLUSIONS

In a subcohort of obese adults, suppression of insulin secretion was associated with loss of body weight and fat mass and with concomitant modulation of caloric intake and macronutrient preference.

Dermatological complications of obesity

Obesity is a health problem of considerable magnitude in the Western world. Dermatological changes have been reported in patients with obesity, including: acanthosis nigricans and skin tags (due to insulin resistance); hyperandrogenism; striae due to over extension; stasis pigmentation due to peripheral vascular disease; lymphedema; pathologies associated with augmented folds; morphologic changes in the foot anatomy due to excess load; and complications that may arise from hospitalization. Acanthosis nigricans plaques can be managed by improved control of hyperinsulinemia; the vitamin D3 analog calcipitriol has also been shown to be effective. Skin tags can be removed by snipping with curved scissors, by cryotherapy or by electrodesiccation. Hyperandrogenism, a result of increased production of endogenous androgens due to increased volumes of adipose tissue (which synthesizes testosterone) and hyperinsulinemia (which increases the production of ovarian androgens) needs to be carefully assessed to ensure disorders such as virilizing tumors and congenital adrenal hyperplasia are treated appropriately. Treatment of hyperandrogenism should be centred on controlling insulin levels; weight loss, oral contraceptive and antiandrogenic therapies are also possible treatment options. The etiology of striae distensae, also known as stretch marks, is yet to be defined and treatment options are unsatisfactory at present; striae rubra and alba have been treated with a pulsed dye laser with marginal success. The relationship between obesity and varicose veins is controversial; symptoms are best prevented by the use of elastic stockings. Itching and inflammation associated with stasis pigmentation, the result of red blood cells escaping into the tissues, can be treated with corticosteroids. Lymphedema is associated with dilatation of tissue channels, reduced tissue oxygenation and provides a culture medium for bacterial growth. Lymphedema treatment is directed towards reducing the limb girth and weight, and the prevention of infection. Intertrigo is caused by friction between skin surfaces, combined with moisture and warmth, resulting in infection. This infection, most commonly candidiasis, is best treated with topical antifungal agents; systemic antifungal therapy may be required in some patients. Excess load on the feet can result in morphological changes that require careful diagnosis; insoles may offer some symptom relief while control of obesity is achieved. Obesity-related dermatoses associated with hospitalization, such as pressure ulcers, diminished wound healing, dermatoses secondary to respiratory conditions, and incontinence, must all be carefully managed with an emphasis on prevention where possible. Recognition and control of the dermatological complications of obesity play an important role in diminishing the morbidity of obesity.

Aspectos fisiológicos do balanço energético

Esta revisão apresenta informações a respeito de substâncias fisiológicas que afetam a homeostase energética. Os autores fizeram uma extensa revisão em relação aos mecanismos fisiológicos que modulam o balanço energético quando administrados central ou perifericamente (por exemplo, nutrientes, monoaminas e peptídeos).

Afferent signals regulating food intake

Food intake is a regulated system. Afferent signals provide information to the central nervous system, which is the centre for the control of satiety or food seeking. Such signals can begin even before food is ingested through visual, auditory and olfactory stimuli. One of the recent interesting findings is the demonstration that there are selective fatty acid taste receptors on the tongue of rodents. The suppression of food intake by essential fatty acids infused into the stomach and the suppression of electrical signals in taste buds reflect activation of a K rectifier channel (K 1.5). In animals that become fat eating a high-fat diet the suppression of this current by linoleic acid is less than that in animals that are resistant to obesity induced by dietary fat. Inhibition of fatty acid oxidation with either mercaptoacetate (which blocks acetyl-CoA dehydrogenase) or methylpalmoxirate will increase food intake. When animals have a choice of food, mercaptoacetate stimulates the intake of protein and carbohydrate, but not fat. Afferent gut signals also signal satiety. The first of these gut signals to be identified was cholecystokinin (CCK). When CCK acts on CCK-A receptors in the gastrointestinal tract, food intake is suppressed. These signals are transmitted by the vagus nerve to the nucleus tractus solitarius and thence to higher centres including the lateral parabrachial nucleus, amygdala, and other sites. Rats that lack the CCK-A receptor become obese, but transgenic mice lacking CCK-A receptors do not become obese. CCK inhibits food intake in human subjects. Enterostatin, the pentapeptide produced when pancreatic colipase is cleaved in the gut, has been shown to reduce food intake. This peptide differs in its action from CCK by selectively reducing fat intake. Enterostatin reduces hunger ratings in human subjects. Bombesin and its human analogue, gastrin inhibitory peptide (also gastrin-insulin peptide), reduce food intake in obese and lean subjects. Animals lacking bombesin-3 receptor become obese, suggesting that this peptide may also be important. Circulating glucose concentrations show a dip before the onset of most meals in human subjects and rodents. When the glucose dip is prevented, the next meal is delayed. The dip in glucose is preceded by a rise in insulin, and stimulating insulin release will decrease circulating glucose and lead to food intake. Pyruvate and lactate inhibit food intake differently in animals that become obese compared with lean animals. Leptin released from fat cells is an important peripheral signal from fat stores which modulates food intake. Leptin deficiency or leptin receptor defects produce massive obesity. This peptide signals a variety of central mechanisms by acting on receptors in the arcuate nucleus and hypothalamus. Pancreatic hormones including glucagon, amylin and pancreatic polypeptide reduce food intake. Four pituitary peptides also modify food intake. Vasopressin decreases feeding. In contrast, injections of desacetyl melanocyte-stimulating hormone, growth hormone and prolactin are associated with increased food intake. Finally, there are a group of miscellaneous peptides that modulate feeding. beta-Casomorphin, a heptapeptide produced during the hydrolysis of casein, stimulates food intake in experimental animals. In contrast, the other peptides in this group, including calcitonin, apolipoprotein A-IV, the cyclized form of histidyl-proline, several cytokines and thyrotropin-releasing hormone, all decrease food intake. Many of these peptides act on gastrointestinal or hepatic receptors that relay messages to the brain via the afferent vagus nerve. As a group they provide a number of leads for potential drug development.

Hypothalamic obesity caused by cranial insult in children: altered glucose and insulin dynamics and reversal by a somatostatin agonist

OBJECTIVE

Hypothalamic obesity is a rare sequela of cranial insult, for which pathogenesis and treatment remain obscure. In rodents ventromedial hypothalamic damage causes hyperphagia, obesity, hyperinsulinism, and insulin resistance. Reduction of insulin secretion in humans may attenuate weight gain.

METHODS

Eight children with intractable obesity after therapy for leukemia or brain tumors underwent oral glucose tolerance testing (OGTT) with simultaneous insulin levels before and after treatment with octreotide for 6 months.

RESULTS

In comparison with a 6-month pre-study observation period, patients exhibited weight loss (+6.0 +/- 0.7 kg vs -4.8 +/- 1.8 kg; P =.04) and decrease in body mass index (+2.1 +/- 0.3 kg/m(2) vs -2.0 +/- 0.7 kg/m(2); P =.0001). Recall calorie count decreased during the 6 months of treatment (P =. 015). OGTT demonstrated biochemical glucose intolerance in 5 of 8 patients initially and in 2 of 7 at study end, whereas insulin response was decreased (281 +/- 47 microU/mL vs 114 +/- 35 microU/mL; P =.04). Percent weight change correlated with changes in insulin response (r = 0.72, P =.012) and changes in plasma leptin r = 0.76, P =.0004).

CONCLUSIONS

Patients with hypothalamic obesity demonstrate excessive insulin secretion. Octreotide administration promoted weight loss, which correlated with reduction in insulin secretion on OGTT and with reduction in leptin levels. Pre-study biochemical glucose tolerance improved in several patients while they were receiving octreotide. These results suggest that normalization of insulin secretion may be an effective therapeutic strategy in this syndrome.