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Dhanapalaratnam R, Issar T, Poynten AM, Milner KL, Kwai NCG, Krishnan AV. Progression of axonal excitability abnormalities with increasing clinical severity of diabetic peripheral neuropathy. Clin Neurophysiol 2024; 160:12-18. [PMID: 38367309 DOI: 10.1016/j.clinph.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 01/18/2024] [Accepted: 02/05/2024] [Indexed: 02/19/2024]
Abstract
OBJECTIVE Diabetic peripheral neuropathy (DPN) is a frequent complication for persons with type 2 diabetes. Previous studies have failed to demonstrate any significant impact of treatment for DPN. The present study assessed the role of axonal ion channel dysfunction in DPN and explored the hypothesis that there may be a progressive change in ion channel abnormalities that varied with disease stage. METHODS Neurophysiological studies were conducted using axonal excitability techniques, a clinical method of assessing ion channel dysfunction. Studies were conducted in 178 persons with type 2 diabetes, with participants allocated into four groups according to clinical severity of neuropathy, assessed using the Total Neuropathy Grade. RESULTS Analysis of excitability data demonstrated a progressive and stepwise reduction in two parameters that are related to the activity of Kv1.1 channels, namely superexcitability and depolarizing threshold electrotonus at 10-20 ms (p < 0.001), and mathematical modelling of axonal excitability findings supported progressive upregulation of Kv1.1 conductances with increasing greater disease severity. CONCLUSION The findings are consistent with a progressive upregulation of juxtaparanodal Kv1.1 conductances with increasing clinical severity of diabetic peripheral neuropathy. SIGNIFICANCE From a translational perspective, the study suggests that blockade of Kv1.1 channels using 4-aminopyridine derivatives such as fampridine may be a potential treatment for DPN.
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Affiliation(s)
- Roshan Dhanapalaratnam
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Neurology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Tushar Issar
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia
| | - Ann M Poynten
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Kerry-Lee Milner
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Natalie C G Kwai
- School of Medical, Indigenous and Health Sciences, University of Wollongong, Australia
| | - Arun V Krishnan
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Neurology, Prince of Wales Hospital, Sydney, NSW 2031, Australia.
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Dhanapalaratnam R, Issar T, Lee ATK, Poynten AM, Milner KL, Kwai NCG, Krishnan AV. Glucagon-like peptide-1 receptor agonists reverse nerve morphological abnormalities in diabetic peripheral neuropathy. Diabetologia 2024; 67:561-566. [PMID: 38189936 DOI: 10.1007/s00125-023-06072-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 11/10/2023] [Indexed: 01/09/2024]
Abstract
AIMS/HYPOTHESIS Diabetic peripheral neuropathy (DPN) is a highly prevalent cause of physical disability. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are used to treat type 2 diabetes and animal studies have shown that glucagon-like peptide-1 (GLP-1) receptors are present in the central and peripheral nervous systems. This study investigated whether GLP-1 RAs can improve nerve structure. METHODS Nerve structure was assessed using peripheral nerve ultrasonography and measurement of tibial nerve cross-sectional area, in conjunction with validated neuropathy symptom scores and nerve conduction studies. A total of 22 consecutively recruited participants with type 2 diabetes were assessed before and 1 month after commencing GLP-1 RA therapy (semaglutide or dulaglutide). RESULTS There was a pathological increase in nerve size before treatment in 81.8% of the cohort (n=22). At 1 month of follow-up, there was an improvement in nerve size in 86% of participants (p<0.05), with 32% returning to normal nerve morphology. A 3 month follow-up study (n=14) demonstrated further improvement in nerve size in 93% of participants, accompanied by reduced severity of neuropathy (p<0.05) and improved sural sensory nerve conduction amplitude (p<0.05). CONCLUSIONS/INTERPRETATION This study demonstrates the efficacy of GLP-1 RAs in improving neuropathy outcomes, evidenced by improvements in mainly structural and morphological measures and supported by electrophysiological and clinical endpoints. Future studies, incorporating quantitative sensory testing and measurement of intraepidermal nerve fibre density, are needed to investigate the benefits for small fibre function and structure.
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Affiliation(s)
- Roshan Dhanapalaratnam
- School of Clinical Medicine, UNSW Sydney, Sydney, NSW, Australia
- Department of Neurology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - Tushar Issar
- School of Clinical Medicine, UNSW Sydney, Sydney, NSW, Australia
| | - Alexandra T K Lee
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - Kerry-Lee Milner
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - Natalie C G Kwai
- School of Medical, Indigenous and Health Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Arun V Krishnan
- School of Clinical Medicine, UNSW Sydney, Sydney, NSW, Australia.
- Department of Neurology, Prince of Wales Hospital, Sydney, NSW, Australia.
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Dhanapalaratnam R, Issar T, Poynten AM, Milner K, Kwai NCG, Krishnan AV. Diagnostic accuracy of nerve ultrasonography for the detection of peripheral neuropathy in type 2 diabetes. Eur J Neurol 2022; 29:3571-3579. [PMID: 36039540 PMCID: PMC9826521 DOI: 10.1111/ene.15534] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 07/05/2022] [Accepted: 07/13/2022] [Indexed: 01/11/2023]
Abstract
BACKGROUND AND PURPOSE Nerve conduction studies (NCS) are the current objective measure for diagnosis of peripheral neuropathy in type 2 diabetes but do not assess nerve structure. This study investigated the utility of peripheral nerve ultrasound as a marker of the presence and severity of peripheral neuropathy in type 2 diabetes. METHODS A total of 156 patients were recruited, and nerve ultrasound was undertaken on distal tibial and distal median nerves. Neuropathy severity was graded using the modified Toronto Clinical Neuropathy Scale (mTCNS) and Total Neuropathy Score (TNS). Studies were undertaken by a single ultrasonographer blinded to nerve conduction results. RESULTS A stepwise increase in tibial nerve cross-sectional area (CSA) was noted with increasing TNS grade (p < 0.001) and each mTCNS quartile (p < 0.001). Regression analysis demonstrated a correlation between tibial nerve CSA and neuropathy severity (p < 0.001). Using receiver operator curve analysis, tibial nerve CSA of >12.88 mm yielded a sensitivity of 70.5% and specificity of 85.7% for neuropathy detection. Binary logistic regression revealed that tibial nerve CSA was a predictor of abnormal sural sensory nerve action potential amplitude (odds ratio = 1.239, 95% confidence interval [CI] = 1.142-1.345) and abnormal neuropathy score (odds ratio = 1.537, 95% confidence interval [CI] = 1.286-1.838). CONCLUSIONS Tibial nerve ultrasound has good specificity and sensitivity for neuropathy diagnosis in type 2 diabetes. The study demonstrates that tibial nerve CSA correlates with neuropathy severity. Future serial studies using both ultrasound and NCS may be useful in determining whether changes in ultrasound occur prior to development of nerve conduction abnormalities and neuropathic symptoms.
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Affiliation(s)
- Roshan Dhanapalaratnam
- Prince of Wales Clinical School, University of New South WalesSydneyNew South WalesAustralia
- Institute of Neurological Sciences, Prince of Wales HospitalSydneyNew South WalesAustralia
| | - Tushar Issar
- Prince of Wales Clinical School, University of New South WalesSydneyNew South WalesAustralia
| | - Ann M. Poynten
- Prince of Wales Clinical School, University of New South WalesSydneyNew South WalesAustralia
- Department of EndocrinologyPrince of Wales HospitalSydneyNew South WalesAustralia
| | - Kerry‐Lee Milner
- Prince of Wales Clinical School, University of New South WalesSydneyNew South WalesAustralia
- Department of EndocrinologyPrince of Wales HospitalSydneyNew South WalesAustralia
| | - Natalie C. G. Kwai
- School of Medical SciencesUniversity of SydneySydneyNew South WalesAustralia
| | - Arun V. Krishnan
- Prince of Wales Clinical School, University of New South WalesSydneyNew South WalesAustralia
- Institute of Neurological Sciences, Prince of Wales HospitalSydneyNew South WalesAustralia
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Klisser J, Tummanapalli SS, Kim J, Chiang JCB, Khou V, Issar T, Naduvilath T, Poynten AM, Markoulli M, Krishnan AV. Automated analysis of corneal nerve tortuosity in diabetes: implications for neuropathy detection. Clin Exp Optom 2022; 105:487-493. [DOI: 10.1080/08164622.2021.1940875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Affiliation(s)
- Jacob Klisser
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | | | - Juno Kim
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | | | - Vincent Khou
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
- Centre for Eye Health, University of New South Wales, Sydney, Australia
| | - Tushar Issar
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Thomas Naduvilath
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, Australia
| | - Maria Markoulli
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
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Issar T, Walker S, Arnold R, Poynten AM, Endre ZH, Krishnan AV. Peripheral nerve morphology and intraneural blood flow in chronic kidney disease with and without diabetes. Muscle Nerve 2022; 65:603-607. [PMID: 35119701 PMCID: PMC9305967 DOI: 10.1002/mus.27513] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 01/24/2022] [Accepted: 01/29/2022] [Indexed: 11/22/2022]
Abstract
Introduction/Aims Sonographic alterations of peripheral nerves in pre‐dialytic kidney disease are yet to be determined. We aimed to assess peripheral nerve cross‐sectional area (CSA) and intraneural blood flow in patients with pre‐dialytic chronic kidney disease (CKD) and diabetic kidney disease (DKD). Methods Subjects with CKD (n = 20) or DKD (n = 20) underwent ultrasound to assess CSA of the median and tibial nerves as well as intraneural blood flow of the median nerve. Blood flow was quantified using maximum perfusion intensity. Neuropathy was assessed using the Total Neuropathy Score. A 6‐m timed walk test was also performed. Healthy controls (n = 28) were recruited for comparison. Results The DKD group had more severe neuropathy (p = .024), larger tibial nerve CSA (p = .002) and greater median nerve blood flow than the CKD group (p = .023). Blood flow correlated with serum potassium in disease groups (r = 0.652, p = .022). Disease groups had larger tibial nerve CSA than controls (p < .05). No blood flow was detected in controls. Tibial nerve enlargement was associated with slower maximal walking speeds in disease groups (r = −0.389, p = .021). Discussion Subjects with DKD demonstrated enlarged tibial nerve CSA and increased median nerve blood flow compared to those with CKD. Elevations in serum potassium were associated with increased blood flow. Sonographic alterations were detectable in pre‐dialytic kidney disease compared to controls, highlighting the utility of ultrasound in the assessment of nerve pathology in these patient groups.
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Affiliation(s)
- Tushar Issar
- Prince of Wales Clinical School, UNSW Sydney, NSW, Australia
| | - Susan Walker
- Prince of Wales Clinical School, UNSW Sydney, NSW, Australia
| | - Ria Arnold
- School of Medical Sciences, UNSW Sydney, NSW, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - Zoltan H Endre
- Department of Nephrology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, UNSW Sydney, NSW, Australia
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Issar T, Tummanapalli SS, Borire AA, Kwai NCG, Poynten AM, Arnold R, Markoulli M, Krishnan AV. Impact of the metabolic syndrome on peripheral nerve structure and function in type 2 diabetes. Eur J Neurol 2021; 28:2074-2082. [PMID: 33682297 DOI: 10.1111/ene.14805] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 02/25/2021] [Indexed: 12/15/2022]
Abstract
BACKGROUND AND PURPOSE There is a strong association between the metabolic syndrome in diabetes and the development of peripheral neuropathy; however, the pathophysiological mechanisms remain unknown. METHODS Participants with type 2 diabetes and metabolic syndrome (T2DM/MetS, n = 89) and type 2 diabetes alone (T2DM; n = 59) underwent median nerve ultrasound and excitability studies to assess peripheral nerve structure and function. A subset of T2DM/MetS (n = 24) and T2DM (n = 22) participants underwent confocal microscopy to assess central and inferior whorl corneal nerve structure. Neuropathy severity was assessed using the modified Toronto Clinical Neuropathy Score (mTCNS). Diabetes groups were similar for age, sex distribution, diabetes duration, hemoglobin A1c , insulin treatment, and renal function. Sixty healthy controls similar for age and sex distribution were recruited for comparison. RESULTS Participants with T2DM/MetS manifested with a greater mTCNS compared to T2DM (p < 0.05). Median nerve cross-sectional area was larger in the T2DM/MetS group compared to the T2DM cohort (p < 0.05). Participants with T2DM/MetS had reductions in central (all p < 0.01) and inferior whorl (all p < 0.05) nerve measures. Compared to T2DM, the T2DM/MetS group demonstrated more severe changes in nerve excitability measures, which was due to reduced sodium channel permeability and sodium-potassium pump function. In comparison, only sodium channel permeability was reduced in the T2DM group. CONCLUSIONS Compared to participants with type 2 diabetes alone, those with diabetes and metabolic syndrome manifested greater alterations in peripheral nerve structure and function, which may be due to reduced function of the sodium-potassium pump.
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Affiliation(s)
- Tushar Issar
- Prince of Wales Clinical School, UNSW Sydney, Sydney, NSW, Australia
| | | | - Adeniyi A Borire
- Prince of Wales Clinical School, UNSW Sydney, Sydney, NSW, Australia
| | - Natalie C G Kwai
- Prince of Wales Clinical School, UNSW Sydney, Sydney, NSW, Australia.,Department of Exercise Physiology, UNSW Sydney, Sydney, NSW, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - Ria Arnold
- Department of Exercise Physiology, UNSW Sydney, Sydney, NSW, Australia
| | - Maria Markoulli
- School of Optometry & Vision Science, UNSW Sydney, Sydney, NSW, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, UNSW Sydney, Sydney, NSW, Australia
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Issar T, Tummanapalli SS, Kwai NCG, Chiang JCB, Arnold R, Poynten AM, Markoulli M, Krishnan AV. Associations between acute glucose control and peripheral nerve structure and function in type 1 diabetes. Diabet Med 2020; 37:1553-1560. [PMID: 32298478 DOI: 10.1111/dme.14306] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/09/2020] [Indexed: 12/13/2022]
Abstract
AIM To examine the associations between continuous overlapping net glycaemic action (CONGA), percentage time in hyperglycaemia (%HG) or normoglycaemia (%NG) and peripheral nerve structure and function in type 1 diabetes. METHODS Twenty-seven participants with type 1 diabetes underwent continuous glucose monitoring followed by corneal confocal microscopy and nerve excitability assessments. CONGA, %HG (> 10.0 mmol/l) and %NG (3.9-10.0 mmol/l) were correlated against corneal nerve fibre length and density in the central cornea and inferior whorl region, corneal microneuromas, and a nerve excitability score while controlling for age, sex, diabetes duration and HbA1c . RESULTS An increase in CONGA [median 2.5 (2.0-3.1) mmol/l] or %HG (mean 46 ± 18%) was associated with a worse nerve excitability score (r = -0.433, P = 0.036 and r = -0.670, P = 0.0012, respectively). By contrast, greater %NG (51 ± 17%) correlated with better nerve excitability scores (r = 0.672, P = 0.0011). Logistic regression revealed that increasing %HG increased the likelihood of abnormal nerve function [odds ratio (OR) 1.11, 95% confidence interval (CI) 1.01-1.23; P = 0.037). An increase in CONGA and %HG were associated with worsening nerve conduction measures, whereas longer %NG correlated with improved nerve conduction variables. CONGA and %HG were associated with inferior whorl corneal nerve fibre length (r = 0.483, P = 0.034 and r = 0.591, P = 0.021, respectively) and number of microneuromas (r = 0.433, P = 0.047 and r = 0.516, P = 0.020, respectively). CONCLUSIONS Short-term measures of glucose control are associated with impaired nerve function and alterations in corneal nerve morphology.
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Affiliation(s)
- T Issar
- Prince of Wales Clinical School, Sydney, NSW, Australia
| | - S S Tummanapalli
- School of Optometry & Vision Science, University of New South Wales, Sydney, NSW, Australia
| | - N C G Kwai
- Prince of Wales Clinical School, Sydney, NSW, Australia
- Department of Exercise Physiology, UNSW-Sydney, Sydney, NSW, Australia
| | - J C B Chiang
- School of Optometry & Vision Science, University of New South Wales, Sydney, NSW, Australia
| | - R Arnold
- Department of Exercise Physiology, UNSW-Sydney, Sydney, NSW, Australia
| | - A M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - M Markoulli
- School of Optometry & Vision Science, University of New South Wales, Sydney, NSW, Australia
| | - A V Krishnan
- Prince of Wales Clinical School, Sydney, NSW, Australia
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Issar T, Yan A, Kwai NCG, Poynten AM, Borire AA, Arnold R, Krishnan AV. Altered peripheral nerve structure and function in latent autoimmune diabetes in adults. Diabetes Metab Res Rev 2020; 36:e3260. [PMID: 31833206 DOI: 10.1002/dmrr.3260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 11/14/2019] [Accepted: 11/27/2019] [Indexed: 11/07/2022]
Abstract
AIM The present study was undertaken to investigate mechanisms of peripheral nerve dysfunction in latent autoimmune diabetes in adults (LADA). MATERIALS AND METHODS Participants with LADA (n = 15) underwent median nerve ultrasonography and nerve excitability to examine axonal structure and function, in comparison to cohorts of type 1 diabetes (n = 15), type 2 diabetes (n = 23) and healthy controls (n = 26). The LADA group was matched for diabetes duration, glycaemic control, and neuropathy severity with the type 1 and type 2 diabetes groups. A validated mathematical model of the human axon was utilized to investigate the pathophysiological basis of nerve dysfunction. RESULTS The most severe changes in nerve structure and function were noted in the LADA group. The LADA cohort demonstrated a significant increase in nerve cross-sectional area compared to type 1 participants and controls. Compared to type 1 and 2 diabetes, measures of threshold electrotonus, which assesses nodal and internodal conductances, were significantly worse in LADA in response to both depolarising currents and hyperpolarising currents. In the recovery cycle, participants with LADA had a significant increase in the relative refractory period. Mathematical modelling of excitability recordings indicated the basis of nerve dysfunction in LADA was different to type 1 and 2 diabetes. CONCLUSIONS Participants with LADA exhibited more severe changes in nerve function and different underlying pathophysiological mechanisms compared to participants with type 1 or 2 diabetes. Intensive management of risk factors to delay the progression of neuropathy in LADA may be required.
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Affiliation(s)
- Tushar Issar
- Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Aimy Yan
- Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Natalie C G Kwai
- Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
- Department of Exercise Physiology, UNSW Sydney, Sydney, New South Wales, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, New South Wales, Australia
| | - Adeniyi A Borire
- Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Ria Arnold
- Department of Exercise Physiology, UNSW Sydney, Sydney, New South Wales, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
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Borire AA, Issar T, Kwai NC, Visser LH, Simon NG, Poynten AM, Kiernan MC, Krishnan AV. Sonographic assessment of nerve blood flow in diabetic neuropathy. Diabet Med 2020; 37:343-349. [PMID: 31338857 DOI: 10.1111/dme.14085] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/22/2019] [Indexed: 12/16/2022]
Abstract
AIMS To undertake sonographic assessment of nerve blood flow in people with Type 2 diabetes and correlate the findings with neuropathy severity scores and electrophysiological measurements. METHODS Median and tibial nerve ultrasound scans were undertaken in 75 people with diabetes and 30 aged-matched controls without diabetes, using a high-resolution linear probe at non-entrapment sites. Nerve blood flow was quantified using power Doppler techniques to obtain the vessel score and the maximum perfusion intensity. Neuropathy severity was assessed using a total neuropathy score. RESULTS Diabetic nerves had higher rates of nerve blood flow detection (28%) compared to the control group (P < 0.0001). Significant correlations were found between nerve blood flow measurements and nerve size (P <0.001), reported sensory symptoms (P < 0.05) and neuropathy severity scores (P < 0.001). The cohort with diabetes had significantly larger median (8.5 ± 0.3 mm2 vs 7.2 ± 0.1 mm2 ; P < 0.05) and tibial nerves (18.0 ± 0.9 mm2 vs 12.8 ± 0.5 mm2 ; P < 0.05) compared with controls. CONCLUSION Peripheral nerve hypervascularity is detectable by ultrasonography in moderate to severe diabetic neuropathy with prominent sensory dysfunction.
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Affiliation(s)
- A A Borire
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - T Issar
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - N C Kwai
- School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - L H Visser
- St Elisabeth Ziekenhuis, Tilburg, Netherlands
| | - N G Simon
- St Vincent's Clinical School, University of New South Wales, Sydney, Australia
| | - A M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Randwick, Australia
| | - M C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - A V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
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Yan A, Issar T, Tummanapalli SS, Markoulli M, Kwai NCG, Poynten AM, Krishnan AV. Relationship between corneal confocal microscopy and markers of peripheral nerve structure and function in Type 2 diabetes. Diabet Med 2020; 37:326-334. [PMID: 30897245 DOI: 10.1111/dme.13952] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/18/2019] [Indexed: 01/03/2023]
Abstract
AIMS To investigate changes in corneal nerve morphology in Type 2 diabetes and to establish relationships between in vivo corneal confocal microscopy and markers of peripheral nerve structure and function. PARTICIPANTS AND METHODS We recruited 57 participants with Type 2 diabetes and 26 healthy controls of similar age and sex distribution. We also recruited a disease control group of 54 participants with Type 1 diabetes. All participants were assessed for distal symmetrical polyneuropathy using the Total Neuropathy Score. In vivo corneal confocal microscopy was used to assess corneal nerve fibre length, corneal nerve fibre density, corneal nerve branch density and inferior whorl length. Peripheral nerve structure was assessed using median nerve ultrasonography. Large fibre function was assessed according to median nerve axonal excitability. Small fibre function was assessed using SudoscanTM and the Survey of Autonomic Symptoms. RESULTS Corneal nerve fibre length, fibre density and branch density and inferior whorl length were significantly lower in individuals with Type 2 diabetes compared to controls (P<0.001 for all). In the Type 2 diabetes cohort, correlations were observed between neuropathy severity and corneal nerve fibre density (P=0.004), corneal nerve branch density (P=0.003), corneal nerve fibre length (P=0.002) and inferior whorl length (P=0.01). Significant correlations were observed between corneal confocal outcomes and axonal excitability measurements. No association was found between corneal confocal microscopy and median nerve cross-sectional area, Sudoscan measurements or the Survey of Autonomic Symptoms. CONCLUSIONS This study demonstrated significant changes in corneal nerves in individuals with Type 2 diabetes. Reductions in corneal nerve measures correlated with increasing neuropathy severity. Associations were found between corneal confocal microscopy and markers of voltage-gated potassium channel function.
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Affiliation(s)
- A Yan
- Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - T Issar
- Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - S S Tummanapalli
- School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia
| | - M Markoulli
- School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia
| | - N C G Kwai
- School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - A M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW, Australia
| | - A V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
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Tummanapalli SS, Issar T, Kwai N, Pisarcikova J, Poynten AM, Krishnan AV, Willcox MDP, Markoulli M. A Comparative Study on the Diagnostic Utility of Corneal Confocal Microscopy and Tear Neuromediator Levels in Diabetic Peripheral Neuropathy. Curr Eye Res 2019; 45:921-930. [DOI: 10.1080/02713683.2019.1705984] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
| | - Tushar Issar
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Natalie Kwai
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Jana Pisarcikova
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | - Ann M. Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, Australia
| | - Arun V. Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Mark D. P. Willcox
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | - Maria Markoulli
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
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Cheung NW, Campbell LV, Fulcher GR, McElduff P, Depczynski B, Acharya S, Carter J, Champion B, Chen R, Chipps D, Flack J, Kinsella J, Layton M, McLean M, Moses RG, Park K, Poynten AM, Pollock C, Scadden D, Tonks KT, Webber M, White C, Wong V, Middleton S. Routine glucose assessment in the emergency department for detecting unrecognised diabetes: a cluster randomised trial. Med J Aust 2019; 211:454-459. [DOI: 10.5694/mja2.50394] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 06/25/2019] [Indexed: 01/17/2023]
Affiliation(s)
- N Wah Cheung
- Westmead Hospital Sydney NSW
- University of Sydney Sydney NSW
| | | | | | | | - Barbara Depczynski
- Prince of Wales Private Hospital Sydney NSW
- Liverpool Hospital Sydney NSW
- Fairfield Hospital Sydney NSW
| | | | | | | | - Roger Chen
- Concord Repatriation General Hospital Sydney NSW
| | | | | | | | | | - Mark McLean
- Western Sydney University School of Medicine Penrith NSW
| | | | | | | | - Carol Pollock
- University of Sydney Sydney NSW
- Royal North Shore Hospital Sydney NSW
| | | | | | | | | | | | - Sandy Middleton
- St Vincent's Health Australia Sydney NSW
- Australian Catholic University Nursing Research Institute Sydney NSW
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Tummanapalli SS, Willcox MD, Issar T, Yan A, Pisarcikova J, Kwai N, Poynten AM, Krishnan AV, Markoulli M. Tear film substance P: A potential biomarker for diabetic peripheral neuropathy. Ocul Surf 2019; 17:690-698. [DOI: 10.1016/j.jtos.2019.08.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 08/14/2019] [Accepted: 08/29/2019] [Indexed: 01/17/2023]
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Tummanapalli SS, Willcox MDP, Issar T, Kwai N, Poynten AM, Krishnan AV, Pisarcikova J, Markoulli M. The Effect of Age, Gender and Body Mass Index on Tear Film Neuromediators and Corneal Nerves. Curr Eye Res 2019; 45:411-418. [DOI: 10.1080/02713683.2019.1666998] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
| | - Mark D. P. Willcox
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | - Tushar Issar
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Natalie Kwai
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Ann M. Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, Australia
| | - Arun V. Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Jana Pisarcikova
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
| | - Maria Markoulli
- School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
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Issar T, Arnold R, Kwai NCG, Walker S, Yan A, Borire AA, Poynten AM, Pussell BA, Endre ZH, Kiernan MC, Krishnan AV. Relative contributions of diabetes and chronic kidney disease to neuropathy development in diabetic nephropathy patients. Clin Neurophysiol 2019; 130:2088-2095. [PMID: 31541986 DOI: 10.1016/j.clinph.2019.08.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 07/04/2019] [Accepted: 08/12/2019] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Chronic kidney disease (CKD) caused by diabetes is known as diabetic kidney disease (DKD). The present study aimed to examine the underlying mechanisms of axonal dysfunction and features of neuropathy in DKD compared to CKD and type 2 diabetes (T2DM) alone. METHODS Patients with DKD (n = 30), CKD (n = 28) or T2DM (n = 40) and healthy controls (n = 41) underwent nerve excitability assessments to examine axonal function. Neuropathy was assessed using the Total Neuropathy Score. A validated mathematical model of human axons was utilised to provide an indication of the underlying causes of nerve pathophysiology. RESULTS Total neuropathy score was significantly higher in patients with DKD compared to those with either CKD or T2DM (p < 0.05). In DKD, nerve excitability measures (S2 accommodation and superexcitability, p < 0.05) were more severely affected compared to both CKD and T2DM and worsened with increasing serum K+ (p < 0.01). Mathematical modelling indicated the basis for nerve dysfunction in DKD was an elevation of extracellular K+ and reductions in Na+ permeability and the hyperpolarisation-activated cation current, which was similar to CKD. CONCLUSIONS Patients with DKD manifested a more severe neuropathy phenotype and shared features of nerve dysfunction to that of CKD. SIGNIFICANCE The CKD, and not diabetes component, appears to underlie axonal pathophysiology in DKD.
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Affiliation(s)
- Tushar Issar
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Ria Arnold
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Natalie C G Kwai
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia; Department of Exercise Physiology, UNSW Sydney, NSW 2052, Australia
| | - Susan Walker
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Aimy Yan
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Adeniyi A Borire
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Bruce A Pussell
- Department of Nephrology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Zoltan H Endre
- Department of Nephrology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia.
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Borire AA, Issar T, Kwai NC, Visser LH, Simon NG, Poynten AM, Kiernan MC, Krishnan AV. Correlation between markers of peripheral nerve function and structure in type 1 diabetes. Diabetes Metab Res Rev 2018; 34:e3028. [PMID: 29858541 DOI: 10.1002/dmrr.3028] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 05/20/2018] [Accepted: 05/28/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND Clinical and experimental studies in patients with type 1 and type 2 diabetes have demonstrated changes in ion channel function and nerve structure. In this study, we investigated the relationship between axonal dysfunction and morphological change in diabetic polyneuropathy by using neuromuscular ultrasound and nerve excitability techniques. We also explored possible differences in this relationship between type 1 and type 2 diabetes. METHODS Nerve ultrasound and corresponding motor excitability studies were undertaken in 110 diabetes patients (50 type 1; 60 type 2) and 60 age-matched controls (30 for each group). Neuropathy severity was assessed by using total neuropathy score. Median and tibial nerve cross-sectional areas were measured at nonentrapment sites by using high-resolution linear probe. RESULTS Median and tibial nerve cross-sectional areas were significantly higher in diabetes patients compared with controls: type 1 (median = 7.6 ± 0.2 mm2 vs 6.3 ± 0.1 mm2 ; tibial = 14.5 ± 0.7 mm2 vs 10.8 ± 0.3 mm2 , P < .05) and type 2 (median = 9.1 ± 0.3 mm2 vs 7.2 ± 0.1 mm2 ; tibial = 18.5 ± 1.0 mm2 vs 12.8 ± 0.5 mm2 , P < .05). In the type 1 cohort, significant correlations were found between nerve cross-sectional area and excitability parameters including resting current-threshold slope (median: r = 0.523, P < .0001; tibial: r = -0.571, P = .004) and depolarizing threshold electrotonus at 90 to 100 ms (median: 0.424, P < .01; tibial: r = 0.435, P = .030). In contrast, there was no relationship between excitability values and nerve cross-sectional area in the type 2 cohort. CONCLUSIONS This study has identified correlation between markers of axonal membrane function and structural abnormalities in peripheral nerves of type 1 diabetes patients. The differential relationship in nerve function and structure between type 1 and type 2 diabetes provides clinical evidence that different pathophysiological mechanisms underlie the development of neuropathy in these patient groups.
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Affiliation(s)
- Adeniyi A Borire
- University of New South Wales, Prince of Wales Clinical School, Sydney, New South Wales, Australia
| | - Tushar Issar
- University of New South Wales, Prince of Wales Clinical School, Sydney, New South Wales, Australia
| | - Natalie C Kwai
- University of New South Wales, School of Medical Sciences, Sydney, New South Wales, Australia
| | - Leo H Visser
- St Elisabeth Ziekenhuis, Tilburg, The Netherlands
| | - Neil G Simon
- University of New South Wales, St Vincent's Clinical School, Sydney, New South Wales, Australia
- University of Sydney, Brain and Mind Centre, Sydney, New South Wales, Australia
| | - Ann M Poynten
- Prince of Wales Hospital, Department of Endocrinology, Sydney, New South Wales, Australia
| | - Matthew C Kiernan
- University of Sydney, Brain and Mind Centre, Sydney, New South Wales, Australia
| | - Arun V Krishnan
- University of New South Wales, Prince of Wales Clinical School, Sydney, New South Wales, Australia
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Issar T, Arnold R, Kwai NC, Pussell BA, Endre ZH, Poynten AM, Kiernan MC, Krishnan AV. The utility of the Total Neuropathy Score as an instrument to assess neuropathy severity in chronic kidney disease: A validation study. Clin Neurophysiol 2018; 129:889-894. [DOI: 10.1016/j.clinph.2018.02.120] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 01/14/2018] [Accepted: 02/04/2018] [Indexed: 10/17/2022]
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Kwai NCG, Arnold R, Poynten AM, Krishnan AV. Association between glycemic variability and peripheral nerve dysfunction in type 1 diabetes. Muscle Nerve 2016; 54:967-969. [PMID: 27465125 DOI: 10.1002/mus.25274] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2016] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Glycemic variability (GV) may be a novel factor in the pathogenesis of diabetic complications. However, the effect of GV on peripheral nerve function has not been explored systematically. METHODS The relationship between GV and acute glucose levels on motor and sensory nerve function in 17 patients with type 1 diabetes mellitus (T1DM) was assessed using continuous glucose monitoring and nerve excitability techniques to provide insight into the behavior of axonal voltage-gated ion channels. The mean amplitude of glycemic excursions (MAGE) was calculated to quantify GV. RESULTS MAGE strongly correlated with excitability markers of altered motor and sensory axonal function, including superexcitability (r = 0.54), S2 accommodation (r = -0.76), minimum current threshold (I/V) slope (r = 0.71), strength duration time constant (r = 0.66), and latency (r = 0.65; P < 0.05). Acute glucose levels did not correlate with markers of axonal function. CONCLUSIONS These findings suggest that GV may be an important mediator of axonal dysfunction in T1DM and a contributing factor in development of diabetic neuropathy. Muscle Nerve, 2016 Muscle Nerve 54: 967-969, 2016.
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Affiliation(s)
- Natalie C G Kwai
- Prince of Wales Clinical School, University of New South Wales Australia, NSW 2052, Sydney, Australia
| | - Ria Arnold
- School of Medical Sciences, University of New South Wales Australia, Sydney, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales Australia, NSW 2052, Sydney, Australia.
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Kwai NCG, Nigole W, Poynten AM, Brown C, Krishnan AV. The Relationship between Dyslipidemia and Acute Axonal Function in Type 2 Diabetes Mellitus In Vivo. PLoS One 2016; 11:e0153389. [PMID: 27078166 PMCID: PMC4831805 DOI: 10.1371/journal.pone.0153389] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 03/29/2016] [Indexed: 01/17/2023] Open
Abstract
Objectives Diabetic peripheral neuropathy (DPN) is a common and debilitating complication of diabetes mellitus. Treatment largely consists of symptom alleviation and there is a need to identify therapeutic targets for prevention and treatment of DPN. The objective of this study was to utilise novel neurophysiological techniques to investigate axonal function in patients with type 2 diabetes and to prospectively determine their relationship to serum lipids in type 2 diabetic patients. Methods Seventy-one patients with type 2 diabetes were consecutively recruited and tested. All patients underwent thorough clinical neurological assessments including nerve conduction studies, and median motor axonal excitability studies. Studies were also undertaken in age matched normal control subjects(n = 42). Biochemical studies, including serum lipid levels were obtained in all patients. Patient excitability data was compared to control data and linear regression analysis was performed to determine the relationship between serum triglycerides and low density lipoproteins and excitability parameters typically abnormal in type 2 diabetic patients. Results Patient mean age was 64.2±2.3 years, mean glycosylated haemoglobin (HbA1c%) was 7.8±0.3%, mean triglyceride concentration was 1.6±0.1 mmol/L and mean cholesterol concentration was 4.1±0.2mmol/L. Compared to age matched controls, median motor axonal excitability studies indicated axonal dysfunction in type 2 diabetic patients as a whole (T2DM) and in a subgroup of the patients without DPN (T2DM-NN). These included reduced percentage threshold change during threshold electrotonus at 10–20ms depolarising currents (TEd10–20ms)(controls 68.4±0.8, T2DM63.9±0.8, T2DM-NN64.8±1.6%,P<0.05) and superexcitability during the recovery cycle (controls-22.5±0.9, T2DM-17.5±0.8, T2DM-NN-17.3±1.6%,P<0.05). Linear regression analysis revealed no associations between changes in axonal function and either serum triglyceride or low density lipoprotein concentration when adjusted for renal function, a separate risk factor for neuropathy development. Our findings indicate that acutely, serum lipids do not exert an acute effect on axonal function in type 2 diabetic patients: TEd(10–20ms)(1.2(-1.4,3.8);P = 0.4) and superexcitability (2.4(-0.05, 4.8);P = 0.06). Conclusions These findings suggest that serum triglyceride levels are not related to axonal function in type 2 diabetic patients. Additional pathogenic mechanisms may play a more substantial role in axonal dysfunction prior to DPN development.
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Affiliation(s)
- Natalie C. G. Kwai
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - William Nigole
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Ann M. Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, Australia
| | - Christopher Brown
- National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, Australia
| | - Arun V. Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
- * E-mail:
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Kwai NCG, Arnold R, Poynten AM, Howells J, Kiernan MC, Lin CSY, Krishnan AV. In vivo evidence of reduced nodal and paranodal conductances in type 1 diabetes. Clin Neurophysiol 2015; 127:1700-1706. [PMID: 26725257 DOI: 10.1016/j.clinph.2015.11.047] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 11/13/2015] [Accepted: 11/29/2015] [Indexed: 12/28/2022]
Abstract
OBJECTIVES Diabetic neuropathy is a debilitating complication of diabetes. Animal models of type 1 diabetes (T1DM) suggest that functional and structural changes, specifically axo-glial dysjunction, may contribute to neuropathy development. The present study sought to examine and characterise early sensory axonal function in T1DM patients in the absence of clinical neuropathy. METHODS Thirty patients with T1DM (15M:15F) without neuropathy underwent median nerve sensory and motor axonal excitability studies to examine axonal function. A verified mathematical model of human motor and sensory axons was used to elucidate the underlying causes of observed alterations. RESULTS Compared to controls (NC), T1DM patients demonstrated significant axonal excitability abnormalities in sensory and motor axons. These included marked reductions in sensory and motor subexcitability during the recovery cycle (T1DM 7.9 ± 0.4:10.4 ± 0.6%, NC 10.4 ± 0.7:15.4 ± 1.2%, P<0.01) and during hyperpolarizing threshold electrotonus at 10-20 ms (T1DM -75.5 ± 0.8:-69.7 ± 0.8%, NC -78.4 ± 1:-72.7 ± 0.9%, P<0.01). Mathematical modelling demonstrated that these changes were due to reduced nodal Na(+) currents, nodal/paranodal K(+) conductances and Na(+)/K(+) pump dysfunction, consistent with axo-glial dysjunction as outlined in animal models of T1DM. CONCLUSIONS The study provided support for the occurrence of early changes in nodal and paranodal conductances in patients with T1DM. SIGNIFICANCE These data indicate that axonal excitability techniques may detect early changes in diabetic patients, providing a window of opportunity for prophylactic intervention in T1DM.
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Affiliation(s)
- Natalie C G Kwai
- Prince of Wales Clinical School, The University of New South Wales, Sydney, Australia
| | - Ria Arnold
- Department of Pharmacology and Physiology, The University of New South Wales, Sydney, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, Australia
| | - James Howells
- Brain and Mind Centre, University of Sydney and Royal Prince Alfred Hospital, Sydney, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Royal Prince Alfred Hospital, Sydney, Australia
| | - Cindy S-Y Lin
- Department of Pharmacology and Physiology, The University of New South Wales, Sydney, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, The University of New South Wales, Sydney, Australia.
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Kwai N, Arnold R, Poynten AM, Lin CSY, Kiernan MC, Krishnan AV. Continuous subcutaneous insulin infusion preserves axonal function in type 1 diabetes mellitus. Diabetes Metab Res Rev 2015; 31:175-82. [PMID: 25066412 DOI: 10.1002/dmrr.2583] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 07/17/2014] [Accepted: 07/18/2014] [Indexed: 01/22/2023]
Abstract
BACKGROUND Diabetic peripheral neuropathy is a common and debilitating complication of diabetes mellitus. Although strict glycaemic control may reduce the risk of developing diabetic peripheral neuropathy, the neurological benefits of different insulin regimens remain relatively unknown. METHODS In the present study, 55 consecutive patients with type 1 diabetes mellitus underwent clinical neurological assessment. Subsequently, 41 non-neuropathic patients, 24 of whom were receiving multiple daily insulin injections (MDII) and 17 receiving continuous subcutaneous insulin infusion (CSII), underwent nerve excitability testing, a technique that assesses axonal ion channel function and membrane potential in human nerves. Treatment groups were matched for glycaemic control, body mass index, disease duration and gender. Neurophysiological parameters were compared between treatment groups and those taken from age and sex-matched normal controls. RESULTS Prominent differences in axonal function were noted between MDII-treated and CSII-treated patients. Specifically, MDII patients manifested prominent abnormalities when compared with normal controls in threshold electrotonus (TE) parameters including depolarizing TE(10-20ms), undershoot and hyperpolarizing TE (90-100 ms) (P < 0.05). Additionally, recovery cycle parameters superexcitability and subexcitability were also abnormal (P < 0.05). In contrast, axonal function in CSII-treated patients was within normal limits when compared with age-matched controls. The differences between the groups were noted in cross-sectional analysis and remained at longitudinal follow-up. CONCLUSIONS Axonal function in type 1 diabetes is maintained within normal limits in patients treated with continuous subcutaneous insulin infusion and not with multiple daily insulin injections. This raises the possibility that CSII therapy may have neuroprotective potential in patients with type 1 diabetes.
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Affiliation(s)
- Natalie Kwai
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales, Sydney, Australia
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Depczynski B, Poynten AM, Fazekas M. Triggers to offering bariatric surgery in the management of type 2 diabetes. Obes Res Clin Pract 2014; 8:e421-5. [PMID: 24925516 DOI: 10.1016/j.orcp.2014.03.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 03/24/2014] [Accepted: 03/29/2014] [Indexed: 01/06/2023]
Abstract
It is unclear how current guidelines suggesting bariatric surgery as a therapeutic option for management of obesity complicated by type 2 diabetes mellitus are utilised in clinical practice. Of 609 patients with T2DM assessed in this study, 147 had a BMI ≥ 35 kg/m2; and of these 147, patients where bariatric surgery had been discussed as compared to those where it had not been discussed, had a higher BMI (44.4 ± 6.8 kg/m2 versus 40.3 ± 5.2 kg/m2, p < 0.005). Diabetes related factors did not differ between the two groups.
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Kwai NCG, Arnold R, Wickremaarachchi C, Lin CSY, Poynten AM, Kiernan MC, Krishnan AV. Effects of axonal ion channel dysfunction on quality of life in type 2 diabetes. Diabetes Care 2013; 36:1272-7. [PMID: 23404298 PMCID: PMC3631837 DOI: 10.2337/dc12-1310] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Pharmacological agents for diabetic peripheral neuropathy (DN) target a number of mechanisms, including sodium channel function and γ-aminobutyric acid-minergic processes. At present, prescription is undertaken on a trial-and-error basis, leading to prolonged medication trials and greater healthcare costs. Nerve-excitability techniques are a novel method of assessing axonal ion channel function in the clinical setting. The aim of this study was to determine the effects of axonal ion channel dysfunction on neuropathy-specific quality-of-life (QoL) measures in DN. RESEARCH DESIGN AND METHODS Fifty-four patients with type 2 diabetes mellitus underwent comprehensive neurologic assessment, nerve-conduction studies, and nerve-excitability assessment. Neuropathy severity was assessed using the Total Neuropathy Score. Neuropathy-specific QoL was assessed using a DN-specific QoL questionnaire (Neuropathy-Specific Quality of Life Questionnaire [NeuroQoL]). Glycosylated hemoglobin and BMI were recorded in all patients. RESULTS NeuroQoL scores indicated significant QoL impairment (mean 9.08 ± 5.93). Strength-duration time constant (SDTC), an excitability parameter reflecting sodium channel function, was strongly correlated with QoL scores (r = 0.545; P < 0.005). SDTC was prolonged in 48.6% of patients who experienced neuropathic symptoms. A significant correlation was also noted between SDTC and neuropathy severity (r = 0.29; P < 0.05). This relationship was strengthened when looking specifically at patients with clinically graded neuropathy (r = 0.366; P < 0.05). CONCLUSIONS The current study has demonstrated an association between markers of sodium channel function and QoL in DN. The study demonstrates that excitability techniques may identify patients in whom altered sodium channel function may be the dominant abnormality. The findings suggest that excitability techniques may have a role in clinical decision making regarding neuropathic treatment prescription.
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Affiliation(s)
- Natalie C G Kwai
- School of Medical Sciences, University of New South Wales, Kensington, Australia
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Affiliation(s)
- Suja Padmanabhan
- From the Department of Endocrinology, Prince of Wales Hospital, New South Wales, Australia
| | - Alessandro S. Zagami
- Institute of Neurological Sciences, Prince of Wales Hospital, New South Wales, Australia
- Prince of Wales Clinical School, University of New South Wales, New South Wales, Australia
| | - Ann M. Poynten
- From the Department of Endocrinology, Prince of Wales Hospital, New South Wales, Australia
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Arnold R, Kwai N, Lin CSY, Poynten AM, Kiernan MC, Krishnan AV. Axonal dysfunction prior to neuropathy onset in type 1 diabetes. Diabetes Metab Res Rev 2013; 29:53-9. [PMID: 23008000 DOI: 10.1002/dmrr.2360] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2012] [Accepted: 09/12/2012] [Indexed: 11/06/2022]
Abstract
BACKGROUND The present study was undertaken to determine whether there were changes evident in axonal membrane function prior to the onset of neuropathy in patients with type 1 and type 2 diabetes. METHODS From a cohort of 110 consecutive referrals, nerve excitability was investigated in 40 diabetic patients without clinical evidence of neuropathy (20 type 1 diabetic patients and 20 type 2 diabetic patients). Groups were matched for gender, disease duration and HbA(1c). Studies were also undertaken in two control groups, younger controls and older controls, matched for age and gender with the diabetic cohorts. RESULTS Subjects with type 1 diabetes demonstrated significant nerve excitability abnormalities when compared with younger normal controls. Specifically, type 1 subjects showed a significant reduction at multiple time points in both depolarising and hyperpolarising threshold electrotonus. Additionally, the relative refractory period was prolonged (type 1, 3.19 ms; younger normal controls, 3.0 ms; p < 0.05) and superexcitability was reduced (type 1, -23.12%; younger normal controls, -26.37%; p < 0.05), consistent with axonal membrane depolarisation. Correlations were identified in type 1 patients between disease duration and nerve excitability parameters, including the relative refractory period (r = -0.533, p < 0.05). In contrast, only minor non-specific changes were noted in the type 2 group. DISCUSSION This study provides clear evidence of altered axonal function in patients with type 1 diabetes in the absence of clinical neuropathy. These findings suggest that altered axonal membrane potential may precede neuropathy onset in type 1 diabetes and as such may indicate a window of opportunity to intervene and potentially reverse axonal membrane dysfunction before the development of irreversible neuropathy.
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Affiliation(s)
- Ria Arnold
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales, Sydney, Australia
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Gan SK, Kriketos AD, Poynten AM, Furler SM, Thompson CH, Kraegen EW, Campbell LV, Chisholm DJ. Insulin Action, Regional Fat, and Myocyte Lipid: Altered Relationships with Increased Adiposity. ACTA ACUST UNITED AC 2012; 11:1295-305. [PMID: 14627749 DOI: 10.1038/oby.2003.176] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Abdominal fat and myocyte triglyceride levels relate negatively to insulin sensitivity, but their interrelationships are inadequately characterized in the overweight. Using recent methods for measuring intramyocyte triglyceride, these relationships were studied in men with a broad range of adiposity. RESEARCH METHODS AND PROCEDURES Myocyte triglyceride content ((1)H-magnetic resonance spectroscopy of soleus and tibialis anterior muscles and biochemical assessment of vastus lateralis biopsies), regional fat distribution (DXA and abdominal magnetic resonance imaging), serum lipids, insulin action (euglycemic hyperinsulinemic clamp), and substrate oxidation rates (indirect calorimetry) were measured in 39 nondiabetic men (35.1 +/- 7.8 years) with a broad range of adiposity (BMI 28.6 +/- 4.1 kg/m(2), range 20.1 to 37.6 kg/m(2)). RESULTS Relationships between insulin-stimulated glucose disposal and regional body fat depots appeared more appropriately described by nonlinear than linear models. When the group was subdivided using median total body fat as the cut-point, insulin-stimulated glucose disposal correlated negatively to all regional body fat measures (all p < or = 0.004), serum triglycerides and free fatty acids (p < 0.02), and both soleus intramyocellular lipid (p = 0.003) and vastus lateralis triglyceride (p = 0.04) in the normal/less overweight group. In contrast, only visceral abdominal fat showed significant negative correlation with insulin-stimulated glucose disposal in more overweight men (r = -0.576, p = 0.01), some of whom surprisingly had lower than expected myocyte lipid levels. These findings persisted when the group was subdivided using different cut-points or measures of adiposity. DISCUSSION Interrelationships among body fat depots, myocyte triglyceride, serum lipids, and insulin action are generally absent with increased adiposity. However, visceral abdominal fat, which corresponds less closely to total adiposity, remains an important predictor of insulin resistance in men with both normal and increased adiposity.
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Affiliation(s)
- Seng Khee Gan
- Metabolism and Diabetes Research Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia
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Li H, Heilbronn LK, Hu D, Poynten AM, Blackburn MA, Shirkhedkar DP, Kaplan WH, Kriketos AD, Ye J, Chisholm DJ. Islet-1: a potentially important role for an islet cell gene in visceral fat. Obesity (Silver Spring) 2008; 16:356-62. [PMID: 18239644 DOI: 10.1038/oby.2007.76] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE To examine differences in gene expression between visceral (VF) and subcutaneous fat (SF) to identity genes of potential importance in regulation of VF. METHODS AND PROCEDURES We compared gene expression (by DNA array and quantitative PCR (qPCR)) in paired VF and SF adipose biopsies from 36 subjects (age 54 +/- 15 years, 15 men/21 women) with varying degrees of adiposity and insulin resistance, in chow and fat fed mice (+/- rosiglitazone treatment) and in c-Cbl(-/-) mice. Gene expression was also examined in 3T3-L1 preadipocytes during differentiation. RESULTS A twofold difference or more was found between VF and SF in 1,343 probe sets, especially for genes related to development, cell differentiation, signal transduction, and receptor activity. Islet-1 (ISL1), a LIM-homeobox gene with important developmental and regulatory function in islet, neural, and cardiac tissue, not previously recognized in adipose tissue was virtually absent in SF but substantially expressed in VF. ISL1 expression correlated negatively with BMI (r = -0.37, P = 0.03), abdominal fat (by dual energy X-ray absorptiometry, r = -0.44, P = 0.02), and positively with circulating adiponectin (r = 0.33, P = 0.04). In diet-induced obese mice, expression was reduced in the presence or absence of rosiglitazone. Correspondingly, expression was increased in the c-Cbl(-/-) mouse, which is lean and insulin sensitive (IS). ISL1 expression was increased sevenfold in 3T3-L1 preadipocytes during early (day 1) differentiation and was reduced by day 2 differentiation. DISCUSSION An important developmental and regulatory gene ISL1 is uniquely expressed in VF, probably in the preadipocyte. Our data suggest that ISL1 may be regulated by adiposity and its role in metabolic regulation merits further study.
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Affiliation(s)
- Haiyan Li
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
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Furler SM, Gan SK, Poynten AM, Chisholm DJ, Campbell LV, Kriketos AD. Relationship of adiponectin with insulin sensitivity in humans, independent of lipid availability. Obesity (Silver Spring) 2006; 14:228-34. [PMID: 16571847 DOI: 10.1038/oby.2006.29] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE To test in humans the hypothesis that part of the association of adiponectin with insulin sensitivity is independent of lipid availability. RESEARCH METHODS AND PROCEDURES We studied relationships among plasma adiponectin, insulin sensitivity (by hyperinsulinemic-euglycemic clamp), total adiposity (by DXA), visceral adiposity (VAT; by magnetic resonance imaging), and indices of lipid available to muscle, including circulating and intramyocellular lipid (IMCL; by 1H-magnetic resonance spectroscopy). Our cohort included normal weight to obese men (n = 36). RESULTS Plasma adiponectin was directly associated with insulin sensitivity and high-density lipoprotein-cholesterol and inversely with plasma triglycerides but not IMCL. These findings are consistent with adiponectin promoting lipid uptake and subsequent oxidation in muscle and inhibiting TG synthesis in the liver. In multiple regression models that also included visceral and total fat, free fatty acids, TGs, and IMCL, either alone or in combination, adiponectin independently predicted insulin sensitivity, consistent with some of its insulin-sensitizing effects being mediated through mechanisms other than modulation of lipid metabolism. Because VAT directly correlated with total fat and all three indices of local lipid availability, free fatty acids, and IMCL, an efficient regression model of insulin sensitivity (R2 = 0.69, p < 0.0001) contained only VAT (part R2 = 0.12, p < 0.002) and adiponectin (part R2 = 0.41, p < 0.0001) as independent variables. DISCUSSION Given the broad range of total adiposity and body fat distribution in our cohort, we suggest that insulin sensitivity is robustly associated with adiponectin and VAT.
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Affiliation(s)
- Stuart M Furler
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, Australia.
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Poynten AM, Gan SK, Kriketos AD, Campbell LV, Chisholm DJ. Circulating fatty acids, non-high density lipoprotein cholesterol, and insulin-infused fat oxidation acutely influence whole body insulin sensitivity in nondiabetic men. J Clin Endocrinol Metab 2005; 90:1035-40. [PMID: 15562033 DOI: 10.1210/jc.2004-0943] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Circulating lipids and tissue lipid depots predict insulin sensitivity. Associations between fat oxidation and insulin sensitivity are variable. We examined whether circulating lipids and fat oxidation independently influence insulin sensitivity. We also examined interrelationships among circulating lipids, fat oxidation, and tissue lipid depots. Fifty-nine nondiabetic males (age, 45.4 +/- 2 yr; body mass index, 29.1 +/- 0.5 kg/m(2)) had fasting circulating nonesterified fatty acids (NEFAs) and lipids measured, euglycemic-hyperinsulinemic clamp for whole body insulin sensitivity [glucose infusion rate (GIR)], substrate oxidation, body composition (determined by dual energy x-ray absorptiometry), and skeletal muscle triglyceride (SMT) measurements. GIR inversely correlated with fasting NEFAs (r = -0.47; P = 0.0002), insulin-infused NEFAs (n = 38; r = -0.62; P < 0.0001), low-density lipoprotein cholesterol (r = -0.50; P < 0.0001), non-high-density lipoprotein cholesterol (r = -0.52; P < 0.0001), basal fat oxidation (r = -0.32; P = 0.03), insulin-infused fat oxidation (r = -0.40; P = 0.02), SMT (r = -0.28; P < 0.05), and central fat (percentage; r = -0.59; P < 0.0001). NEFA levels correlated with central fat, but not with total body fat or SMT. Multiple regression analysis showed non-high-density lipoprotein cholesterol, fasting NEFAs, insulin-infused fat oxidation, and central fat to independently predict GIR, accounting for approximately 60% of the variance. Circulating fatty acids, although closely correlated with central fat, independently predict insulin sensitivity. Insulin-infused fat oxidation independently predicts insulin sensitivity across a wide range of adiposity. Therefore, lipolytic regulation as well as amount of central fat are important in modulating insulin sensitivity.
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Affiliation(s)
- A M Poynten
- Diabetes and Obesity, Garvan Institute of Medical Research, Sydney 2010, Australia.
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Poynten AM, Markovic TP, Maclean EL, Furler SM, Freund J, Chisholm DJ, Campbell LV. Fat oxidation, body composition and insulin sensitivity in diabetic and normoglycaemic obese adults 5 years after weight loss. Int J Obes (Lond) 2003; 27:1212-8. [PMID: 14513069 DOI: 10.1038/sj.ijo.0802393] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE To investigate whether normal glucose-tolerant and type II diabetic overweight adults differ in response to weight regain with regard to substrate oxidation and metabolic parameters. METHODS A total of 15 overweight-obese subjects: seven normal glucose tolerant (NGT) and eight with type II diabetes (DM) were restudied 5 y after significant weight loss. Prediet, after 28 days calorie restriction and at 5 y, subjects were characterised for weight, height, waist-to-hip ratio (WHR) and body composition by dual-energy X-ray absorptiometry. Fasting glucose, insulin, leptin and lipid levels were measured and subjects underwent euglycaemic-hyperinsulinaemic clamp (insulin 0.25 U/kg/h for 150 min). Indirect calorimetry was performed resting and in the final 30 min of the clamp. Dietary assessment was by 4-day diet-diary. RESULTS Both NGT and DM groups regained weight at 5 y and were not different to prediet. Total body fat (%) and WHR were higher at 5 y compared to prediet in both groups. Fasting glucose was increased in NGT subjects at 5 y, and fasting insulin was higher in both groups at 5 y compared to prediet. Insulin sensitivity (GIR) was similar at 5 y compared to prediet, but at 5 y DM subjects were more insulin resistant than NGT subjects. At 5 y, both DM and NGT groups had significantly reduced basal fat oxidation and no significant suppression of fat oxidation with insulin. Clamp respiratory quotient levels at 5 y were significantly higher in NGT compared to DM subjects. CONCLUSION Reduced basal fat oxidation, and reduced variation in substrate oxidation in response to insulin develop with fat regain and fasting hyperinsulinaemia in both NGT and DM obese adults.
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Affiliation(s)
- A M Poynten
- Garvan Institute of Medical Research, Sydney, Australia.
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Poynten AM, Gan SK, Kriketos AD, O'Sullivan A, Kelly JJ, Ellis BA, Chisholm DJ, Campbell LV. Nicotinic acid-induced insulin resistance is related to increased circulating fatty acids and fat oxidation but not muscle lipid content. Metabolism 2003; 52:699-704. [PMID: 12800094 DOI: 10.1016/s0026-0495(03)00030-1] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Insulin resistance is associated with increased circulating lipids and skeletal muscle lipid content. Chronic nicotinic acid (NA) treatment reduces insulin sensitivity and provides a model of insulin resistance. We hypothesized that the reduction in insulin sensitivity occurs via elevation of circulating nonesterified fatty acids (NEFAs) and an increase in intramyocellular lipid (IMCL). A total of 15 nondiabetic males (mean age 27.4 +/- 1.6 years) were treated with NA (500 mg daily for 1 week, 1 g daily for 1 week). Insulin sensitivity (glucose infusion rate [GIR]) was determined pre- and post-NA by euglycemic-hyperinsulinemic clamp. Substrate oxidation was determined by indirect calorimetry. Skeletal muscle lipid was assessed by estimation of long-chain acyl-CoA (LCACoA) and triglyceride (TG) content and by (1)H-magnetic resonance spectroscopy quantification of IMCL (n = 11). NA reduced GIR (P =.03) and nonoxidative glucose disposal (P <.01) and increased fasting NEFAs (P =.01). The decrease in GIR related significantly to the increase in fasting NEFAs (r(2) =.30, P =.03). The intrasubject increase in basal and clamp fat oxidation correlated with the decrease in GIR (r(2) =.45, P <.01 and r(2) =.63, P <.01). There were no significant changes in muscle LCACoA, TG, or IMCL content. Therefore, induction of insulin resistance by NA occurs with increased availability of circulating fatty acids to muscle rather than with increased muscle lipid content.
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Affiliation(s)
- Ann M Poynten
- Garvan Institute of Medical Research, Sydney, Australia
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Kriketos AD, Furler SM, Gan SK, Poynten AM, Chisholm DJ, Campbell LV. Multiple indexes of lipid availability are independently related to whole body insulin action in healthy humans. J Clin Endocrinol Metab 2003; 88:793-8. [PMID: 12574215 DOI: 10.1210/jc.2002-020848] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
An increase in muscle lipid content has been postulated to relate closely to the evolution of insulin resistance. We aimed to test whether the multiple indexes of lipid supply within man [namely, circulating triglycerides, skeletal muscle triglycerides (SMT), total and central fat mass, and circulating leptin] were independent predictors of insulin resistance, or whether triglycerides from different sources are additive in their influence on whole body insulin sensitivity. Whole body insulin sensitivity, body composition, and SMT content were determined in 49 sedentary, nondiabetic males (age, 20-74 yr; body mass index, 20-38 kg/m(2)). Insulin sensitivity was inversely associated with central abdominal fat (r(2) = 0.38; P < 0.0001), total body fat (r(2) = 0.21; P = 0.0003), SMT content (r(2) = 0.16; P = 0.005), and fasting triglycerides (r(2) = 0.24; P = 0.0003), nonesterified free fatty acid (r(2) = 0.19; P = 0.002), and leptin (r(2) = 0.35; P < 0.0001) levels. However, only central abdominal fat was significantly related to SMT content (r(2) = 0.10; P = 0.03). SMT content, circulating triglycerides, and measurements of total or central adiposity were independent predictors of whole body insulin sensitivity.
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Affiliation(s)
- Adamandia D Kriketos
- Diabetes and Metabolism Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, New South Wales 2010, Australia.
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Furler SM, Poynten AM, Kriketos AD, Lowy AJ, Ellis BA, Maclean EL, Courtenay BG, Kraegen EW, Campbell LV, Chisholm DJ. Independent influences of central fat and skeletal muscle lipids on insulin sensitivity. Obes Res 2001; 9:535-43. [PMID: 11557834 DOI: 10.1038/oby.2001.70] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
OBJECTIVE Insulin resistance is closely associated with two disparate aspects of lipid storage: the intracellular lipid content of skeletal muscle and the magnitude of central adipose beds. Our aim was to determine their relative contribution to impaired insulin action. RESEARCH METHODS AND PROCEDURES Eighteen older (56 to 75 years of age) men were studied before elective knee surgery. Insulin sensitivity (M/Delta I) was determined by hyperinsulinemic-euglycemic clamp. Central abdominal fat (CF) was assessed by DXA. Skeletal muscle was excised at surgery and assayed for content of metabolically active long-chain acyl-CoA esters (LCAC). RESULTS Significant inverse relationships were observed between LCAC and M/Delta I (R(2) = 0.34, p = 0.01) and between CF and M/Delta I (R(2) = 0.38, p = 0.006), but not between CF and LCAC (R(2) = 0.0005, p = 0.93). In a multiple regression model (R(2) = 0.71, p < 0.0001), both CF (p = 0.0006) and LCAC (p = 0.0009) were independent statistical predictors of M/Delta I. Leptin levels correlated inversely with M/Delta I (R(2) = 0.60, p = 0.0002) and positively with central (R(2) = 0.41, p = 0.006) and total body fat (R(2) = 0.63, p = 0.0001). DISCUSSION The mechanisms by which altered lipid metabolism in skeletal muscle influences insulin action may not be related directly to those linking central fat and insulin sensitivity. In particular, it is unlikely that muscle accumulation of lipids directly derived from labile central fat depots is a principal contributor to peripheral insulin resistance. Instead, our results imply that circulating factors, other than nonesterified fatty acids or triglyceride, mediate between central fat depots and skeletal muscle tissue. Leptin was not exclusively associated with central fat, but other factors, secreted specifically from central fat cells, could modulate muscle insulin sensitivity.
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Affiliation(s)
- S M Furler
- Diabetes and Metabolism Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney NSW, Australia
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Lapsys NM, Kriketos AD, Lim-Fraser M, Poynten AM, Lowy A, Furler SM, Chisholm DJ, Cooney GJ. Expression of genes involved in lipid metabolism correlate with peroxisome proliferator-activated receptor gamma expression in human skeletal muscle. J Clin Endocrinol Metab 2000; 85:4293-7. [PMID: 11095470 DOI: 10.1210/jcem.85.11.6973] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Peroxisome proliferator-activated receptor gamma (PPAR-gamma) activation in adipose tissue is known to regulate genes involved in adipocyte differentiation and lipid metabolism. However, the role of PPAR-gamma in muscle remains unclear. To examine the potential regulation of genes by PPAR-gamma in human skeletal muscle, we used semiquantitative RT-PCR to determine the expression of PPAR-gamma, lipoprotein lipase (LPL), muscle carnitine palmitoyl transferase-1 (mCPT1), fatty acid-binding protein (FABP), carnitine acylcarnitine transferase (CACT), and glucose transporter-4 (GLUT4) in freeze-dried muscle samples from 14 male subjects. These samples were dissected free of adipose and other tissue contamination, as confirmed by minimal or absent adipsin expression. Between individuals, the messenger ribonucleic acid concentration of PPAR-gamma varied up to 3-fold, whereas LPL varied up to 6.5-fold, mCPT1 13-fold, FABP 4-fold, CACT 4-fold, and GLUT4 up to 3-fold. The expression of LPL (r2 = 0.54; P = 0.003), mCPT1 (r2 = 0.42; P = 0.012), and FABP (r2 = 0.324; P = 0.034) all correlated significantly with PPAR-gamma expression in the same samples. No significant correlation was observed between the expression of CACT and PPAR-gamma or between GLUT4 and PPAR-gamma. These findings demonstrate a relationship between PPAR-gamma expression and the expression of other genes of lipid metabolism in muscle and support the hypothesis that PPAR-gamma activators such as the antidiabetic thiazolidinediones may regulate fatty acid metabolism in skeletal muscle as well as in adipose tissue.
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Affiliation(s)
- N M Lapsys
- Metabolism and Diabetes Research Group, The Garvan Institute of Medical Research, Sydney, New South Wales, Australia.
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