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Corneal Confocal Microscopy Identifies Small Nerve Fibre Damage in Patients with Hypertriglyceridemia. J Clin Lipidol 2022; 16:463-471. [DOI: 10.1016/j.jacl.2022.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 03/01/2022] [Accepted: 04/24/2022] [Indexed: 11/20/2022]
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Abstract
Diabetes polyneuropathy is an important complication of diabetes polyneuropathy, and its notable sequelae of foot ulceration, autonomic dysfunction, and neuropathic pain are associated with significant morbidity and mortality. Despite the major impact on quality of life and health economic costs, it remains underdiagnosed until late in its natural history, and there is lack of any intervention that can reverse its clinical progress. Assessment of small fiber neuropathy (SFN) in diabetes offers an opportunity to detect abnormalities at an early stage so that both interventional studies and preventative measures can be enacted to prevent progression to the devastating complications of foot ulceration and cardiac dysautonomic death. Over the last two decades, significant advances have been made in understanding the pathophysiology of diabetes neuropathy and its assessment. In this review, we discuss limitations of the screening methods recommended in current clinical guidelines which are based on large nerve fiber assessments. Thereafter, we discuss in detail the various methods currently available to assess small fiber structure and function and examine their individual strength and limitations. Finally, we discuss the reasons why despite the considerable body of evidence available, legislators and global experts have yet to incorporate the assessment of SFN as routine clinical surveillance in diabetes management. We hope that these insights will stimulate further discussion and be instrumental in the early adoption of these methods so as to reduce the burden of complications arising due to diabetes polyneuropathy.
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Affiliation(s)
- Sanjeev Sharma
- Diabetes Trails unit, Ipswich Hospital
(ESNEFT), Ipswich, UK
| | - Prashanth Vas
- Department of Diabetes, Kings College
Hospital, London, UK
| | - Gerry Rayman
- Diabetes Trails unit, Ipswich Hospital
(ESNEFT), Ipswich, UK
- Gerry Rayman, MD, Diabetes Trials Unit,
Department of Diabetes & Endocrinology, Ipswich Hospital, ESNEFT, Heath
Road, Ipswich, Suffolk IP4 5RH, UK.
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Abstract
PURPOSE OF REVIEW Hyperlipidaemia is associated with the development of neuropathy. Indeed, a mechanistic link between altered lipid metabolism and peripheral nerve dysfunction has been demonstrated in a number of experimental and clinical studies. Furthermore, post hoc analyses of clinical trials of cholesterol and triglyceride-lowering pharmacotherapy have shown reduced rates of progression of diabetic neuropathy. Given, there are currently no FDA approved disease-modifying therapies for diabetic neuropathy, modulation of lipids may represent a key therapeutic target for the treatment of diabetic nerve damage. This review summarizes the current evidence base on the role of hyperlipidaemia and lipid lowering therapy on the development and progression of peripheral neuropathy. RECENT FINDINGS A body of literature supports a detrimental effect of dyslipidaemia on nerve fibres resulting in somatic and autonomic neuropathy. The case for an important modulating role of hypertriglyceridemia is stronger than for low-density lipoprotein cholesterol (LDL-C) in relation to peripheral neuropathy. This is reflected in the outcomes of clinical trials with the different therapeutic agents targeting hyperlipidaemia reporting beneficial or neutral effects with statins and fibrates. The potential concern with the association between proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor therapy and cognitive decline raised the possibility that extreme LDL-C lowering may result in neurodegeneration. However, studies in murine models and data from small observational studies indicate an association between increased circulating PCSK9 levels and small nerve fibre damage with a protective effect of PCSK9i therapy against small fibre neuropathy. Additionally, weight loss with bariatric surgery leads to an improvement in peripheral neuropathy and regeneration of small nerve fibres measured with corneal confocal microscopy in people with obesity with or without type 2 diabetes. These improvements correlate inversely with changes in triglyceride levels. SUMMARY Hyperlipidaemia, particularly hypertriglyceridemia, is associated with the development and progression of neuropathy. Lipid modifying agents may represent a potential therapeutic option for peripheral neuropathy. Post hoc analyses indicate that lipid-lowering therapies may halt the progression of neuropathy or even lead to regeneration of nerve fibres. Well designed randomized controlled trials are needed to establish if intensive targeted lipid lowering therapy as a part of holistic metabolic control leads to nerve fibre regeneration and improvement in neuropathy symptoms.
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Affiliation(s)
- Zohaib Iqbal
- Faculty of Biology, Medicine and Health, University of Manchester
- Department of Endocrinology, Diabetes and Metabolism, Peter Mount Building, Manchester Royal Infirmary, Manchester University NHS Foundation Trust, Manchester, UK
| | - Bilal Bashir
- Department of Endocrinology, Diabetes and Metabolism, Peter Mount Building, Manchester Royal Infirmary, Manchester University NHS Foundation Trust, Manchester, UK
| | - Maryam Ferdousi
- Faculty of Biology, Medicine and Health, University of Manchester
- Department of Endocrinology, Diabetes and Metabolism, Peter Mount Building, Manchester Royal Infirmary, Manchester University NHS Foundation Trust, Manchester, UK
| | - Alise Kalteniece
- Faculty of Biology, Medicine and Health, University of Manchester
| | - Uazman Alam
- Department of Cardiovascular & Metabolic Medicine, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Rayaz A Malik
- Faculty of Biology, Medicine and Health, University of Manchester
- Department of Cardiovascular & Metabolic Medicine, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Handrean Soran
- Faculty of Biology, Medicine and Health, University of Manchester
- Department of Endocrinology, Diabetes and Metabolism, Peter Mount Building, Manchester Royal Infirmary, Manchester University NHS Foundation Trust, Manchester, UK
- Weill-Cornell Medicine-Qatar, Doha, Qatar
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Sharma S, Tobin V, Vas PRJ, Malik RA, Rayman G. The influence of age, anthropometric and metabolic variables on LDIFLARE and corneal confocal microscopy in healthy individuals. PLoS One 2018. [PMID: 29518115 PMCID: PMC5843248 DOI: 10.1371/journal.pone.0193452] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Introduction The laser Doppler imaging (LDI) FLARE and corneal confocal microscopy (CCM) are reliable markers of small fibre function (SFF) and structure (SFS), respectively, but the impact of potential confounding variables needs to be defined. The objective of this study was to determine the influence of age, anthropometric and biochemical variables on LDI and CCM. Methods 80 healthy volunteers (43 males) (age: 39.7±15.2 yrs.) underwent LDIFLARE and CCM assessment and the effect of age, anthropometric and biochemical variables was determined using multivariate analysis. Results There was an age-related decline in LDIFLARE (0.07cm2/yr; R2 = 0.669; p = <0.0001) and CCM parameters (CNFD: 0.05 fibres/mm2 /yr; R2 = 0.590; p = <0.0001, CNBD: 0.06 branches/mm2/yr; R2 = 0.549; p = 0.001and CNFL 0.07 mm/mm2/yr; R2 = 0.369; p = 0.009). BMI did not influence SFF (p = 0.08) but had a significant independent association with CNFD (p = 0.01). Fasting triglycerides (TG) independently influenced the LDIFLARE (βc:-0.204; p = 0.008) and all CCM indices (βc:-0.191 to -0.243; p = <0.05). HbA1c was significantly associated with CNFD only (p = 0.001) but not with LDIFLARE, CNBD or CNFL (p = ≥0.05). Blood pressure and total cholesterol were not associated with LDIFLARE or any CCM parameters. There was a significant correlation between LDIFLARE and all CCM parameters (p = ≤0.01). Conclusions This study shows that in healthy controls, both SFF measured by LDIFLARE and SFS assessed by CCM showed a significant inverse correlation with age and triglycerides, perhaps suggesting the use of age-specific normative values when interpreting these outcomes. Furthermore, this study shows that in healthy controls, despite measuring different neural parameters, both methods correlated significantly with each other.
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Affiliation(s)
- Sanjeev Sharma
- Diabetes Research Unit, The Ipswich Hospital NHS Trust, Ipswich, United Kingdom
| | - Victoria Tobin
- Diabetes Research Unit, The Ipswich Hospital NHS Trust, Ipswich, United Kingdom
| | - Prashanth R. J. Vas
- Department of Diabetes, The Kings College NHS Foundation Trust, London, United Kingdom
| | - Rayaz A. Malik
- Weill Cornell Medicine-Qatar, Doha, Qatar & Institute of Cardiovascular Medicine, University of Manchester, Manchester, United Kingdom
| | - Gerry Rayman
- Diabetes Research Unit, The Ipswich Hospital NHS Trust, Ipswich, United Kingdom
- * E-mail:
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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] [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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Chan ACY, Wilder-Smith EP. Small fiber neuropathy: Getting bigger! Muscle Nerve 2016; 53:671-82. [PMID: 26872938 DOI: 10.1002/mus.25082] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/10/2016] [Indexed: 12/13/2022]
Abstract
Etiological and clinical heterogeneity of small fiber neuropathy (SFN) precludes a unifying approach and necessitates reliance on recognizable clinical syndromes. Symptoms of SFN arise from dysfunction in nociception, temperature, and autonomic modalities. This review focuses on SFN involving nociception and temperature, examining epidemiology, etiology, clinical presentation, diagnosis, pathophysiology, and management. Prevalence of SFN is 52.95 per 100,000 population, and diabetes and idiopathic are the most common etiologies. Dysesthesia, allodynia, pain, burning, and coldness sensations frequently present in a length-dependent pattern. Additional autonomic features in gastrointestinal, urinary, or cardiovascular systems are frequent but poorly objectified. SFN is diagnosed by intraepidermal nerve fiber density and quantitative sensory and autonomic tests in combination with normal nerve conduction. Pathophysiological understanding centers on sodium channel dysfunction, and genetic forms are beginning to be understood. Treatment is directed at the underlying etiology supported by symptomatic treatment using antidepressants and anticonvulsants. Little is known about long-term outcomes, and systematic cohort studies are needed.
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Affiliation(s)
- Amanda C Y Chan
- Division of Neurology, National University Hospital, Level 10 Tower Block, University Medicine Cluster, 1E Kent Ridge Road, 119228, Singapore
| | - Einar P Wilder-Smith
- Division of Neurology, National University Hospital, Level 10 Tower Block, University Medicine Cluster, 1E Kent Ridge Road, 119228, Singapore.,Neurology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Vas PRJ, Sharma S, Rayman G. Distal Sensorimotor Neuropathy: Improvements in Diagnosis. Rev Diabet Stud 2015; 12:29-47. [PMID: 26676660 PMCID: PMC5397982 DOI: 10.1900/rds.2015.12.29] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 04/29/2015] [Accepted: 04/30/2015] [Indexed: 01/01/2023] Open
Abstract
Neurological complications of diabetes are common, affecting up to 50% of people with diabetes. In these patients, diabetic sensorimotor neuropathy (DSPN) is by far the most frequent complication. Detecting DSPN has traditionally been a clinical exercise that is based on signs and symptoms. However, the appearance of morphometric and neurophysiological techniques along with composite scoring systems and new screening tools has induced a paradigm change in the detection and stratification of DSPN and our understanding of its natural history and etiopathogenesis. These newer techniques have provided further evidence that changes in small nerve fiber structure and function precede large fiber changes in diabetes. Although useful, the challenge for the use of these new techniques will be their sensitivity and specificity when widely adopted and ultimately, their ability to demonstrate improvement when pathogenic mechanisms are corrected. Concurrently, we have also witnessed an emergence of simpler screening tools or methods that are mainly aimed at quicker detection of large fiber neuropathy in the outpatient setting. In this review, we have focused on techniques and tools that receive particular attention in the current literature, their use in research and potential use in the clinical environment.
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Affiliation(s)
| | | | - Gerry Rayman
- Ipswich Hospital NHS Trust, Ipswich, United Kingdom
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