Across-species benefits of adrenalectomy on congenital generalized lipoatrophic diabetes: a review

Two adrenalectomies py -45erformed fourteen years apart notoriously alleviated insulin resistance in a female teenager with Congenital Generalized Lipoatrophy (CGL, 1988) and in a murine model of CGL (2002). Following a successful therapeutic trial with anti-glucocorticoids, we performed the first surgical procedure on an 18-year-old girl. Before surgery, the anti-glucocorticoid therapy produced a rapid and striking drop in fasting serum insulin levels (from over 400 to 7.0 mU/L) and a slower -but impressive- fall in fasting serum triglycerides from 7,400 to 220-230 mg/dL. In contrast, fasting serum glucose levels dropped more slowly, from 225-290 to 121-138 mg/dL. Two weeks following total adrenalectomy, the fasting serum glucose level was 98 mg/dL, with a corresponding serum insulin level of 10 mU/L. During an Oral Glucose Tolerance Test, the 2-hour serum glucose was 210 mg/dL, and serum insulin values during the test did not exceed 53 mU/L. In 2002, the A-ZIP/F1 hypoleptinemic mouse had its adrenal glands removed. Even though this CGL model does not respond well to leptin replacement, an infusion of recombinant leptin reduced the characteristic hypercorticosteronemia of this murine model of CGL. Adrenalectomy in this transgenic mouse improved insulin sensitivity in the liver and muscle. In summary, adrenalectomy -in both a human and a mouse case of CGL- limited adipose tissue exposure to corticosteroid action and led to a notorious metabolic improvement. On a broader scenario, given that leptin restrains the adrenal axis, the reduced leptin activity of the leptin resistance displayed by obese subjects should lead to adrenal axis overactivity. This overactivity should result in elevated serum levels of free cortisol, free fatty acids, and glycerol. In this manner, leptin resistance should lead to peripheral (adipose tissue, liver, and muscle) insulin resistance and islet beta-cell apoptosis, paving the way to Type 2 diabetes.

Lipoatrophic diabetes in familial partial lipodystrophy type 2: From insulin resistance to diabetes

AIM

Subjects with Familial Partial Lipodystrophy type 2 (FPLD2) are at high risk to develop diabetes. To better understand the natural history and variability of this disease, we studied glucose tolerance, insulin response to an oral glucose load, and metabolic markers in the largest cohort to date of subjects with FPLD2 due to the same LMNA variant.

METHODS

A total of 102 patients aged > 18 years, with FPLD2 due to the LMNA 'Reunionese' variant p.(Thr655Asnfs*49) and 22 unaffected adult relatives with normal glucose tolerance (NGT) were enrolled. Oral Glucose Tolerance Tests (OGTT) with calculation of derived insulin sensitivity and secretion markers, and measurements of HbA1c, C-reactive protein, leptin, adiponectin and lipid profile were performed.

RESULTS

In patients with FPLD2: 65% had either diabetes (41%) or prediabetes (24%) despite their young age (median: 39.5 years IQR 29.0-50.8) and close-to-normal BMI (median: 25.5 kg/m² IQR 23.1-29.4). Post-load OGTT values revealed insulin resistance and increased insulin secretion in patients with FPLD2 and NGT, whereas patients with diabetes were characterized by decreased insulin secretion. Impaired glucose tolerance with normal fasting glucose was present in 86% of patients with prediabetes. Adiponectin levels were decreased in all subjects with FPLD2 and correlated with insulin sensitivity markers.

CONCLUSIONS

OGTT reveals early alterations of glucose and insulin metabolism in patients with FPLD2, and should be systematically performed before excluding a diagnosis of prediabetes or diabetes to adapt medical care. Decreased adiponectin is an early marker of the disease. Adiponectin replacement therapy warrants further study in FPLD2.

Loss of thymidine phosphorylase activity disrupts adipocyte differentiation and induces insulin-resistant lipoatrophic diabetes

BACKGROUND

Thymidine phosphorylase (TP), encoded by the TYMP gene, is a cytosolic enzyme essential for the nucleotide salvage pathway. TP catalyzes the phosphorylation of the deoxyribonucleosides, thymidine and 2'-deoxyuridine, to thymine and uracil. Biallelic TYMP variants are responsible for Mitochondrial NeuroGastroIntestinal Encephalomyopathy (MNGIE), an autosomal recessive disorder characterized in most patients by gastrointestinal and neurological symptoms, ultimately leading to death. Studies on the impact of TYMP variants in cellular systems with relevance to the organs affected in MNGIE are still scarce and the role of TP in adipose tissue remains unexplored.

METHODS

Deep phenotyping was performed in three patients from two families carrying homozygous TYMP variants and presenting with lipoatrophic diabetes. The impact of the loss of TP expression was evaluated using a CRISPR-Cas9-mediated TP knockout (KO) strategy in human adipose stem cells (ASC), which can be differentiated into adipocytes in vitro. Protein expression profiles and cellular characteristics were investigated in this KO model.

RESULTS

All patients had TYMP loss-of-function variants and first presented with generalized loss of adipose tissue and insulin-resistant diabetes. CRISPR-Cas9-mediated TP KO in ASC abolished adipocyte differentiation and decreased insulin response, consistent with the patients' phenotype. This KO also induced major oxidative stress, altered mitochondrial functions, and promoted cellular senescence. This translational study identifies a new role of TP by demonstrating its key regulatory functions in adipose tissue.

CONCLUSIONS

The implication of TP variants in atypical forms of monogenic diabetes shows that genetic diagnosis of lipodystrophic syndromes should include TYMP analysis. The fact that TP is crucial for adipocyte differentiation and function through the control of mitochondrial homeostasis highlights the importance of mitochondria in adipose tissue biology.

[Recognize rare diseases by the adipose tissue : Lipodystrophy-actually simple but nevertheless often overlooked]

Lipodystrophy (LD) syndromes are a group of rare and heterogeneous diseases characterized by a congenital deficiency or acquired loss of adipose tissue. Due to the resulting disorder of metabolism, sometimes severe sequelae can develop, such as hypertriglyceridemia, marked insulin resistance and early manifestation of type 2 diabetes, recurrent pancreatitis, fatty liver disease and liver fibrosis. Lipodystrophies are clinically recognizable due to the complete lack of subcutaneous adipose tissue or a conspicuous pattern of the distribution of body fat. Acanthosis nigricans in slimly built persons, a high fasting triglyceride level and elevated concentrations of liver enzymes as well as a positive history of pancreatitis can be indications of LD.

Brown fat lipoatrophy and increased visceral adiposity through a concerted adipocytokines overexpression induces vascular insulin resistance and dysfunction

In this study, we analyzed the role played by concerted expression of adipocytokines associated with brown fat lipoatrophy and increased visceral adiposity on triggering vascular insulin resistance and dysfunction in brown adipose tissue (BAT) insulin receptor knockout (BATIRKO) mice. In addition, we assessed whether vascular insulin resistance may aggravate vascular damage. The 52-wk-old, but not 33-wk-old, BATIRKO mice had a significant decrease of BAT mass associated with a significant increase of visceral white adipose tissue (WAT) mass, without changes in body weight. Brown fat lipoatrophy and increased visceral adiposity enhanced the concerted expression of adipocytokines (TNF-α, leptin, and plasminogen activator inhibitor 1) and nuclear factor-κB binding activity in BAT and visceral WAT, mainly in the gonadal depot, and aorta. Although those mice showed insulin sensitivity in the liver and skeletal muscle, insulin signaling in WAT (gonadal depot) and aorta was markedly impaired. Treatment with anti-TNF-α antibody impaired the inflammatory activity in visceral adipose tissue, attenuated insulin resistance in WAT and aorta and induced glucose tolerance. Finally, 52-wk-old BATIRKO mice showed vascular dysfunction, macrophage infiltration, oxidative stress, and a significant increase of gene markers of endothelial activation and inflammation, the latter effect being totally reverted by anti-TNF-α antibody treatment. Our results suggest that brown fat lipoatrophy and increased visceral adiposity through the concerted overexpression of cytoadipokines induces nuclear factor-κB-mediated inflammatory signaling, vascular insulin resistance, and vascular dysfunction. Inhibition of inflammatory activity by anti-TNF-α antibody treatment attenuates vascular insulin resistance and impairs gene expression of vascular dysfunction markers.

Lipodystrophies

The lipodystrophies are rare disorders characterized by selective but variable loss of adipose tissue. Metabolic complications, such as insulin resistance, diabetes mellitus, hypertriglyceridemia, and fatty liver, increase in severity with the extent of fat loss. The lipodystrophies can be classified into two major types: familial and acquired. The main subtypes of familial lipodystrophies are congenital generalized lipodystrophy, an autosomal recessive disorder characterized by near complete lack of metabolically active adipose tissue from birth, and familial partial lipodystrophy, Dunnigan type, an autosomal dominant disorder characterized by loss of subcutaneous fat from the extremities at puberty and excess fat accumulation in the face and neck. Recently, a gene for congenital generalized lipodystrophy was localized to chromosome 9q34, and a gene for familial partial lipodystrophy, Dunnigan type, to chromosome 1q21-22; the genes, however, remain to be identified. Patients with acquired generalized lipodystrophy have generalized loss of subcutaneous fat, but those with acquired partial lipodystrophy have fat loss limited to the face, trunk, and upper extremities. Both varieties occur approximately three times more often in women, begin during childhood, and have underlying autoimmunity. Patients infected with the human immunodeficiency virus (HIV) who are receiving therapy that includes HIV-1 protease inhibitors have been reported to develop a lipodystrophy characterized by loss of subcutaneous fat from the extremities and face but excess fat deposition in the neck and trunk. Localized lipodystrophies can be caused by drugs, pressure, panniculitis, or unknown mechanisms. Current management of patients includes cosmetic surgery, diet, and drug therapy for control of diabetes and dyslipidemia.

Syndrome of lipoatrophic diabetes, vitamin D resistant rickets, and persistent Müllerian ducts in a Turkish boy born to consanguineous parents

Congenital lipodystrophy (MIM 269700), persistent Müllerian ducts (MIM 261550), and vitamin D resistant rickets (MIM 277440) were observed in an 8 1/2-year-old boy born to consanguineous parents. Measurements of hormone sensitive lipase activity from a sample of the suprapubic fat depot were normal. Although the insulin receptor appeared normal (including autophosphorylation), insulin action, assessed by induction of total mRNA, was decreased. The vitamin D receptor was normal in size and amount, with a slight decrease in affinity for 1,25(OH)2D3. Induction of 24-hydroxylase, used as a measure of responsiveness to 1,25(OH)2D3, was only mildly defective. Assessment of anti-Müllerian hormone (AMH) failed to show any abnormalities explaining the persistent Müllerian ducts. We speculate that a defect in general hormone action common to 1,25(OH)2D3, insulin, and AMH may exist in this patient although we can not exclude the unlikely possibility that he is homozygous for two or three individually rare mutations.