Background and Objective: Hyperleptinemia is supposed to play a causal role in the development of... more Background and Objective: Hyperleptinemia is supposed to play a causal role in the development of obesity-associated hypertension, possibly via increased sympathetic tone. Hence patients with congenital leptin deficiency should be hypotensive and their low blood pressure should increase under leptin substitution. Subjects and Methods: To test this assumption, we examined ambulatory blood pressure, resting heart rate, Schellong test results, cold pressor test results, heart rate variability, catecholamine metabolites, and aldosterone levels in 6 patients with congenital leptin deficiency before as well as 2–7 days and 7–14 months after the start of leptin substitution. Ambulatory blood pressure was also examined in 3 patients with biallelic disease-causing variants in the leptin receptor gene. Results: Contrary to our expectations, even before leptin substitution, 1 patient with biallelic leptin receptor gene variants and 4 patients with leptin deficiency had been suffering from hype...
Human obesity is associated with impaired central insulin signaling, and in very rare cases, seve... more Human obesity is associated with impaired central insulin signaling, and in very rare cases, severe obesity can be caused by congenital leptin deficiency. In such patients, leptin replacement results in substantial weight loss and improvement in peripheral metabolism. In a leptin-deficient patient, we investigated the impact of leptin substitution on central insulin action, as quantified by changes in neuronal activity after intranasal insulin application. This was assessed before and during the 1st year of metreleptin substitution. After only 1 year, treatment with metreleptin reestablishes brain insulin sensitivity, particularly in the hypothalamus and, to a lesser degree, in the prefrontal cortex. Results are depicted in comparison with a control group. In our patient, brain activation changes were accompanied by substantial weight loss, reduced visceral adipose tissue, reduced intrahepatic lipid content, and improved whole-body insulin sensitivity. Leptin replacement and weight ...
To identify the underlying gene mutation in a large consanguineous Pakistani family. Methods: Th... more To identify the underlying gene mutation in a large consanguineous Pakistani family. Methods: This is an observational descriptive study carried out at the Department of Biochemistry, Shifa International Hospital, Quaid-i-Azam University, and Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, Pakistan from 2013-2016. Genomic DNA of all recruited family members was extracted and the Trusight one sequencing panel was used to assess genes associated with a neuro-muscular phenotype. Comparative modeling of mutated and wild-type protein was carried out by PyMOL tool. Results: Clinical investigations of an affected individual showed typical features of Miyoshi myopathy (MM) like elevated serum creatine kinase (CK) levels, distal muscle weakness, myopathic changes in electromyography (EMG) and muscle histopathology. Sequencing with the Ilumina Trusight one sequencing panel revealed a novel 22 nucleotide duplication (CTTCAACTTGTTTGACTC...
Numerous studies confirmed the association ofFTO(fat mass and obesity associated gene) common var... more Numerous studies confirmed the association ofFTO(fat mass and obesity associated gene) common variant, rs9939609, with obesity in European populations. However, studies in Asian populations revealed conflicting results. We examined the association of rs9939609 variant ofFTOgene with obesity and obesity-related anthropometric and metabolic parameters in Pakistani population. Body weight, height, waist circumference, hip circumference, and blood pressure (BP) were measured. BMI and waist-to-hip ratio (WHR) were calculated. Levels of fasting blood glucose (FBG), insulin, leptin, and leptin receptors were measured by enzyme linked immunosorbent assay (ELISA), and homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. The results showed association ofFTOgene, rs9939609, with obesity in females (>18 years of age).FTOminor allele increased the risk of obesity by 2.8 times (95% CI = 1.3–6.0) in females. This allele showed association with body weight, BMI, waist cir...
Am J Hum Genet. 2013 Oct 3;93(4):727-34. doi: 10.1016/j.ajhg.2013.08.002. Epub 2013 Sep 12.
Koehler K, Malik M, Mahmood S, Gießelmann S, Beetz C, Hennings JC, Huebner AK, Grahn A, Reunert J... more Koehler K, Malik M, Mahmood S, Gießelmann S, Beetz C, Hennings JC, Huebner AK, Grahn A, Reunert J, Nürnberg G, Thiele H, Altmüller J, Nürnberg P, Mumtaz R, Babovic-Vuksanovic D, Basel-Vanagaite L, Borck G, Brämswig J, Mühlenberg R, Sarda P, Sikiric A, Anyane-Yeboa K, Zeharia A, Ahmad A, Coubes C, Wada Y, Marquardt T, Vanderschaeghe D, Van Schaftingen E, Kurth I, Huebner A, Hübner CA.
Source
Division of Endocrinology and Diabetes, Children's Hospital, Technical University Dresden, Dresden 01307, Germany.
Abstract
In guanosine diphosphate (GDP)-mannose pyrophosphorylase A (GMPPA), we identified a homozygous nonsense mutation that segregated with achalasia and alacrima, delayed developmental milestones, and gait abnormalities in a consanguineous Pakistani pedigree. Mutations in GMPPA were subsequently found in ten additional individuals from eight independent families affected by the combination of achalasia, alacrima, and neurological deficits. This autosomal-recessive disorder shows many similarities with triple A syndrome, which is characterized by achalasia, alacrima, and variable neurological deficits in combination with adrenal insufficiency. GMPPA is a largely uncharacterized homolog of GMPPB. GMPPB catalyzes the formation of GDP-mannose, which is an essential precursor of glycan moieties of glycoproteins and glycolipids and is associated with congenital and limb-girdle muscular dystrophies with hypoglycosylation of α-dystroglycan. Surprisingly, GDP-mannose pyrophosphorylase activity was unchanged and GDP-mannose levels were strongly increased in lymphoblasts of individuals with GMPPA mutations. This suggests that GMPPA might serve as a GMPPB regulatory subunit mediating feedback inhibition of GMPPB instead of displaying catalytic enzyme activity itself. Thus, a triple-A-like syndrome can be added to the growing list of congenital disorders of glycosylation, in which dysregulation rather than mere enzyme deficiency is the basal pathophysiological mechanism.
... the Pakistani population Muhammad Imran1, Saqib Mahmood2*, Rashid Hussain3, Noman B Abid4, Kh... more ... the Pakistani population Muhammad Imran1, Saqib Mahmood2*, Rashid Hussain3, Noman B Abid4, Khalid P Lone1 ... of Veterinary and Animal Sciences Lahore (UVAS) with the help of Dr. Tanveer Hussain ... Babar, ME, Farid, A., Benkel, BF, Ahmad, J., Nadeem, A., Imran, M., 2009 ...
Background and Objective: Hyperleptinemia is supposed to play a causal role in the development of... more Background and Objective: Hyperleptinemia is supposed to play a causal role in the development of obesity-associated hypertension, possibly via increased sympathetic tone. Hence patients with congenital leptin deficiency should be hypotensive and their low blood pressure should increase under leptin substitution. Subjects and Methods: To test this assumption, we examined ambulatory blood pressure, resting heart rate, Schellong test results, cold pressor test results, heart rate variability, catecholamine metabolites, and aldosterone levels in 6 patients with congenital leptin deficiency before as well as 2–7 days and 7–14 months after the start of leptin substitution. Ambulatory blood pressure was also examined in 3 patients with biallelic disease-causing variants in the leptin receptor gene. Results: Contrary to our expectations, even before leptin substitution, 1 patient with biallelic leptin receptor gene variants and 4 patients with leptin deficiency had been suffering from hype...
Human obesity is associated with impaired central insulin signaling, and in very rare cases, seve... more Human obesity is associated with impaired central insulin signaling, and in very rare cases, severe obesity can be caused by congenital leptin deficiency. In such patients, leptin replacement results in substantial weight loss and improvement in peripheral metabolism. In a leptin-deficient patient, we investigated the impact of leptin substitution on central insulin action, as quantified by changes in neuronal activity after intranasal insulin application. This was assessed before and during the 1st year of metreleptin substitution. After only 1 year, treatment with metreleptin reestablishes brain insulin sensitivity, particularly in the hypothalamus and, to a lesser degree, in the prefrontal cortex. Results are depicted in comparison with a control group. In our patient, brain activation changes were accompanied by substantial weight loss, reduced visceral adipose tissue, reduced intrahepatic lipid content, and improved whole-body insulin sensitivity. Leptin replacement and weight ...
To identify the underlying gene mutation in a large consanguineous Pakistani family. Methods: Th... more To identify the underlying gene mutation in a large consanguineous Pakistani family. Methods: This is an observational descriptive study carried out at the Department of Biochemistry, Shifa International Hospital, Quaid-i-Azam University, and Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, Pakistan from 2013-2016. Genomic DNA of all recruited family members was extracted and the Trusight one sequencing panel was used to assess genes associated with a neuro-muscular phenotype. Comparative modeling of mutated and wild-type protein was carried out by PyMOL tool. Results: Clinical investigations of an affected individual showed typical features of Miyoshi myopathy (MM) like elevated serum creatine kinase (CK) levels, distal muscle weakness, myopathic changes in electromyography (EMG) and muscle histopathology. Sequencing with the Ilumina Trusight one sequencing panel revealed a novel 22 nucleotide duplication (CTTCAACTTGTTTGACTC...
Numerous studies confirmed the association ofFTO(fat mass and obesity associated gene) common var... more Numerous studies confirmed the association ofFTO(fat mass and obesity associated gene) common variant, rs9939609, with obesity in European populations. However, studies in Asian populations revealed conflicting results. We examined the association of rs9939609 variant ofFTOgene with obesity and obesity-related anthropometric and metabolic parameters in Pakistani population. Body weight, height, waist circumference, hip circumference, and blood pressure (BP) were measured. BMI and waist-to-hip ratio (WHR) were calculated. Levels of fasting blood glucose (FBG), insulin, leptin, and leptin receptors were measured by enzyme linked immunosorbent assay (ELISA), and homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. The results showed association ofFTOgene, rs9939609, with obesity in females (>18 years of age).FTOminor allele increased the risk of obesity by 2.8 times (95% CI = 1.3–6.0) in females. This allele showed association with body weight, BMI, waist cir...
Am J Hum Genet. 2013 Oct 3;93(4):727-34. doi: 10.1016/j.ajhg.2013.08.002. Epub 2013 Sep 12.
Koehler K, Malik M, Mahmood S, Gießelmann S, Beetz C, Hennings JC, Huebner AK, Grahn A, Reunert J... more Koehler K, Malik M, Mahmood S, Gießelmann S, Beetz C, Hennings JC, Huebner AK, Grahn A, Reunert J, Nürnberg G, Thiele H, Altmüller J, Nürnberg P, Mumtaz R, Babovic-Vuksanovic D, Basel-Vanagaite L, Borck G, Brämswig J, Mühlenberg R, Sarda P, Sikiric A, Anyane-Yeboa K, Zeharia A, Ahmad A, Coubes C, Wada Y, Marquardt T, Vanderschaeghe D, Van Schaftingen E, Kurth I, Huebner A, Hübner CA.
Source
Division of Endocrinology and Diabetes, Children's Hospital, Technical University Dresden, Dresden 01307, Germany.
Abstract
In guanosine diphosphate (GDP)-mannose pyrophosphorylase A (GMPPA), we identified a homozygous nonsense mutation that segregated with achalasia and alacrima, delayed developmental milestones, and gait abnormalities in a consanguineous Pakistani pedigree. Mutations in GMPPA were subsequently found in ten additional individuals from eight independent families affected by the combination of achalasia, alacrima, and neurological deficits. This autosomal-recessive disorder shows many similarities with triple A syndrome, which is characterized by achalasia, alacrima, and variable neurological deficits in combination with adrenal insufficiency. GMPPA is a largely uncharacterized homolog of GMPPB. GMPPB catalyzes the formation of GDP-mannose, which is an essential precursor of glycan moieties of glycoproteins and glycolipids and is associated with congenital and limb-girdle muscular dystrophies with hypoglycosylation of α-dystroglycan. Surprisingly, GDP-mannose pyrophosphorylase activity was unchanged and GDP-mannose levels were strongly increased in lymphoblasts of individuals with GMPPA mutations. This suggests that GMPPA might serve as a GMPPB regulatory subunit mediating feedback inhibition of GMPPB instead of displaying catalytic enzyme activity itself. Thus, a triple-A-like syndrome can be added to the growing list of congenital disorders of glycosylation, in which dysregulation rather than mere enzyme deficiency is the basal pathophysiological mechanism.
... the Pakistani population Muhammad Imran1, Saqib Mahmood2*, Rashid Hussain3, Noman B Abid4, Kh... more ... the Pakistani population Muhammad Imran1, Saqib Mahmood2*, Rashid Hussain3, Noman B Abid4, Khalid P Lone1 ... of Veterinary and Animal Sciences Lahore (UVAS) with the help of Dr. Tanveer Hussain ... Babar, ME, Farid, A., Benkel, BF, Ahmad, J., Nadeem, A., Imran, M., 2009 ...
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Papers by Saqib Mahmood
Source
Division of Endocrinology and Diabetes, Children's Hospital, Technical University Dresden, Dresden 01307, Germany.
Abstract
In guanosine diphosphate (GDP)-mannose pyrophosphorylase A (GMPPA), we identified a homozygous nonsense mutation that segregated with achalasia and alacrima, delayed developmental milestones, and gait abnormalities in a consanguineous Pakistani pedigree. Mutations in GMPPA were subsequently found in ten additional individuals from eight independent families affected by the combination of achalasia, alacrima, and neurological deficits. This autosomal-recessive disorder shows many similarities with triple A syndrome, which is characterized by achalasia, alacrima, and variable neurological deficits in combination with adrenal insufficiency. GMPPA is a largely uncharacterized homolog of GMPPB. GMPPB catalyzes the formation of GDP-mannose, which is an essential precursor of glycan moieties of glycoproteins and glycolipids and is associated with congenital and limb-girdle muscular dystrophies with hypoglycosylation of α-dystroglycan. Surprisingly, GDP-mannose pyrophosphorylase activity was unchanged and GDP-mannose levels were strongly increased in lymphoblasts of individuals with GMPPA mutations. This suggests that GMPPA might serve as a GMPPB regulatory subunit mediating feedback inhibition of GMPPB instead of displaying catalytic enzyme activity itself. Thus, a triple-A-like syndrome can be added to the growing list of congenital disorders of glycosylation, in which dysregulation rather than mere enzyme deficiency is the basal pathophysiological mechanism.
Source
Division of Endocrinology and Diabetes, Children's Hospital, Technical University Dresden, Dresden 01307, Germany.
Abstract
In guanosine diphosphate (GDP)-mannose pyrophosphorylase A (GMPPA), we identified a homozygous nonsense mutation that segregated with achalasia and alacrima, delayed developmental milestones, and gait abnormalities in a consanguineous Pakistani pedigree. Mutations in GMPPA were subsequently found in ten additional individuals from eight independent families affected by the combination of achalasia, alacrima, and neurological deficits. This autosomal-recessive disorder shows many similarities with triple A syndrome, which is characterized by achalasia, alacrima, and variable neurological deficits in combination with adrenal insufficiency. GMPPA is a largely uncharacterized homolog of GMPPB. GMPPB catalyzes the formation of GDP-mannose, which is an essential precursor of glycan moieties of glycoproteins and glycolipids and is associated with congenital and limb-girdle muscular dystrophies with hypoglycosylation of α-dystroglycan. Surprisingly, GDP-mannose pyrophosphorylase activity was unchanged and GDP-mannose levels were strongly increased in lymphoblasts of individuals with GMPPA mutations. This suggests that GMPPA might serve as a GMPPB regulatory subunit mediating feedback inhibition of GMPPB instead of displaying catalytic enzyme activity itself. Thus, a triple-A-like syndrome can be added to the growing list of congenital disorders of glycosylation, in which dysregulation rather than mere enzyme deficiency is the basal pathophysiological mechanism.