Innervation Patterns of Autonomic Axons in the Human Endocrine Pancreas

“Our results are in line with the notion that there are considerable species variations in the mechanisms of autonomic neurotransmission (Lundberg, 1996), and they reiterate that results from rodent studies should be extrapolated with caution to the human situation (see also Bosco et al., 2010; Brissova et al., 2005; C…”

“Many studies have implicated the autonomic nervous system in islet function and glucose homeostasis (reviewed in (Ahrén, 2000; Brunicardi et al., 1995; Gilon and Henquin, 2001; Havel and Taborsky, 1989; Satin and Kinard, 1998; Woods and Porte, 1974).”

“Our results are in line with the notion that there are considerable species variations in the mechanisms of autonomic neurotransmission (Lundberg, 1996), and they reiterate that results from rodent studies should be extrapolated with caution to the human situation (see also Bosco et al., 2010; Brissova et al., 2005; C…”

“Consistent with how secretion is regulated by sympathetic nerves in exocrine glands (Holst et al., 1989; Love et al., 2007; Proctor and Carpenter, 2007), sympathetic innervation may modulate insulin secretion not directly by acting on secretory cells but indirectly by controlling blood flow (Atef…”

“Many studies have implicated the autonomic nervous system in islet function and glucose homeostasis (reviewed in Ahré n, 2000; Brunicardi et al., 1995; Gilon and Henquin, 2001; Havel and Taborsky, 1989; Satin and Kinard, 1998; Woods and Porte, 1974).”

“Acetylcholinesterase is not considered a reliable marker for cholinergic cells (Mesulam et al., 1984).”

“Many studies have implicated the autonomic nervous system in islet function and glucose homeostasis (reviewed in Ahré n, 2000; Brunicardi et al., 1995; Gilon and Henquin, 2001; Havel and Taborsky, 1989; Satin and Kinard, 1998; Woods and Porte, 1974).”

“Our results are in line with the notion that there are considerable species variations in the mechanisms of autonomic neurotransmission (Lundberg , 1996), and they reiterate that results from rodent studies should be extrapolated with caution to the human situation (see also Bosco et al., 2010;…”

“Thus, a direct neural influence on insulin secretion during feeding may be relatively small in humans (Ahrén and Holst, 2001; Teff et al., 1991).”

“Nonetheless, attributing these axons to the parasympathetic system is difficult and would require axonal tracing studies to rule out the possibility that they represent intrinsic axons or other axons from the enteric system (Kirchgessner and Gershon, 1990; Prinz et al., 1983).”

“Many studies have implicated the autonomic nervous system in islet function and glucose homeostasis (reviewed in Ahré n, 2000; Brunicardi et al., 1995; Gilon and Henquin, 2001; Havel and Taborsky, 1989; Satin and Kinard, 1998; Woods and Porte, 1974).”

“We used a marker found in all axon terminals of vertebrate neurons, synapsin I/II (De Camilli et al., 1990), which labels all axonal terminals containing conventional transmitters stored in small synaptic vesicles.”

“Selective stimulation of islet innervation is difficult (Ahrén et al., 1987; Bloom and Edwards, 1984).”

“Data are presented as mean ± SEM close associations with axons and axonal varicosities that define autonomic effector junctions (Burnstock, 2009).”

“Our results are in line with the notion that there are considerable species variations in the mechanisms of autonomic neurotransmission (Lundberg, 1996), and they reiterate that results from rodent studies should be extrapolated with caution to the human situation (see also Bosco et al., 2010; Brissova et al., 2005; C…”

“…showing that patients who have undergone pancreas transplantation (and thus have denervated islets) remain euglycemic without therapy (Blackman et al., 1992; Diem et al., 1990; Madsbad et al., 1994; Pozza et al., 1985), although losses in fine-tuning of islet function may have escaped scrutiny.”

“Thus, a direct neural influence on insulin secretion during feeding may be relatively small in humans (Ahrén and Holst, 2001; Teff et al., 1991).”

“Indeed, studies show that the classical cholinergic nerve fibers cannot explain all of the vagal effects in the endocrine pancreas (Ahrén et al., 1986; Havel et al., 1997; Holst et al., 1981).”

“Indeed, studies show that the classical cholinergic nerve fibers cannot explain all of the vagal effects in the endocrine pancreas (Ahrén et al., 1986; Havel et al., 1997; Holst et al., 1981).”

“Many studies have implicated the autonomic nervous system in islet function and glucose homeostasis (reviewed in Ahré n, 2000; Brunicardi et al., 1995; Gilon and Henquin, 2001; Havel and Taborsky, 1989; Satin and Kinard, 1998; Woods and Porte, 1974).”

“Many studies have implicated the autonomic nervous system in islet function and glucose homeostasis (reviewed in Ahré n, 2000; Brunicardi et al., 1995; Gilon and Henquin, 2001; Havel and Taborsky, 1989; Satin and Kinard, 1998; Woods and Porte, 1974).”

“, 2007; Proctor and Carpenter, 2007), sympathetic innervation may modulate insulin secretion not directly by acting on secretory cells but indirectly by controlling blood flow (Atef et al., 1992, 1996; Jansson and Hellerström, 1986).”

“Consistent with how secretion is regulated by sympathetic nerves in exocrine glands (Holst et al., 1989; Love et al., 2007; Proctor and Carpenter, 2007), sympathetic innervation may modulate insulin secretion not directly by acting on secretory cells but indirectly by controlling blood flow (Atef…”

“Because this neuropeptide is a putative cotransmitter in parasympathetic nerves, human islets may receive noncholinergic parasympathetic input, as described for other organs (Mazzone and Canning, 2002).”

“…showing that patients who have undergone pancreas transplantation (and thus have denervated islets) remain euglycemic without therapy (Blackman et al., 1992; Diem et al., 1990; Madsbad et al., 1994; Pozza et al., 1985), although losses in fine-tuning of islet function may have escaped scrutiny.”

“Indeed, manipulating adrenergic signaling has strong effects on islet blood flow and insulin secretion in rats (Atef et al., 1996; Jansson et al., 1989; Pettersson et al., 2009).”

“…nerves in exocrine glands (Holst et al., 1989; Love et al., 2007; Proctor and Carpenter, 2007), sympathetic innervation may modulate insulin secretion not directly by acting on secretory cells but indirectly by controlling blood flow (Atef et al., 1992, 1996; Jansson and Hellerströ m, 1986).”

“Axons containing vasoactive intestinal peptide, however, have been shown to innervate human islets (Bishop et al., 1980; (F–”

“A close relationship between the nervous system and the regulation of plasma glucose was revealed early by Claude Bernard (Bernard, 1855), and Paul Langerhans recognized a rich innervation of the pancreatic islets since their discovery (Langerhans and Morrison, 1937).”

“Indeed, studies show that the classical cholinergic nerve fibers cannot explain all of the vagal effects in the endocrine pancreas (Ahrén et al., 1986; Havel et al., 1997; Holst et al., 1981).”

“This interpretation of our results is supported by studies showing that patients who have undergone pancreas transplantation (and thus have denervated islets) remain euglycemic without therapy (Blackman et al., 1992; Diem et al., 1990; Madsbad et al., 1994; Pozza et al., 1985), although losses in fine-tuning of islet…”

“Indeed, studies show that the classical cholinergic nerve fibers cannot explain all of the vagal effects in the endocrine pancreas (Ahré n et al., 1986; Havel et al., 1997; Holst et al., 1981).”

“Sympathetic inhibition of insulin secretion in humans (Gilliam et al., 2007 ) may thus be mediated by noradrenaline-induced vasoconstriction and reduced perfusion of the islet, thereby diminishing insulin release into the circulation.”

“Nonetheless, attributing these axons to the parasympathetic system is difficult and would require axonal tracing studies to rule out the possibility that they represent intrinsic axons or other axons from the enteric system (Kirchgessner and Gershon, 1990; Prinz et al., 1983).”

“Axons containing vasoactive intestinal peptide, however, have been shown to innervate human islets (Bishop et al., 1980; Fahrenkrug et al., 1987).”

“Selective stimulation of islet innervation is difficult (Ahrén et al., 1987; Bloom and Edwards, 1984).”

“Previous studies reported the presence of neuronal axons expressing acetylcholinesterase or diverse neuropeptides such as galanin or vasoactive intestinal peptide in human islets (Ahré n et al., 1991; Amenta et al., 1983; Bishop et al., 1980; Ding et al., 1997; Shimosegawa et al., 1993).”

“Few studies, however, have described the structural innervation of the human islet, and these studies are not comprehensive (Ahrén et al., 1991; Amenta et al., 1983; Bishop et al., 1980; Ding et al., 1997; Shimosegawa et al., 1993).”

“Indeed, manipulating adrenergic signaling has strong effects on islet blood flow and insulin secretion in rats (Atef et al., 1996; Jansson et al., 1989; Pettersson et al., 2009).”

“Consistent with how secretion is regulated by sympathetic nerves in exocrine glands (Holst et al., 1989; Love et al., 2007; Proctor and Carpenter, 2007), sympathetic innervation may modulate insulin secretion not directly by acting on secretory cells but indirectly by controlling blood flow (Atef…”

“Previous studies reported the presence of neuronal axons expressing acetylcholinesterase or diverse neuropeptides such as galanin or vasoactive intestinal peptide in human islets (Ahré n et al., 1991; Amenta et al., 1983; Bishop et al., 1980; Ding et al., 1997; Shimosegawa et al., 1993).”

“Indeed, manipulating adrenergic signaling has strong effects on islet blood flow and insulin secretion in rats (Atef et al., 1996; Jansson et al., 1989; Pettersson et al., 2009).”

“Previous studies reported the presence of neuronal axons expressing acetylcholinesterase or diverse neuropeptides such as galanin or vasoactive intestinal peptide in human islets (Ahré n et al., 1991; Amenta et al., 1983; Bishop et al., 1980; Ding et al., 1997; Shimosegawa et al., 1993).”

“8).(127,146) Recently, it was suggested that the pattern of parasympathetic innervation in humans is different from the one in mice.”

“Mice are widely used as models for islet disease, despite marked differences between rodent and primate islet architecture and innervation [31-34].”

“Peri- and intra-islet ECMs are also intimately associated with the autonomic nerve fibers that follow the islet vasculature (Mei et al. 2002; Rodriguez-Diaz et al. 2011).”

“University Hospitals (CER 05-028 [05-065]) (Geneva, Switzerland).”

“In mouse islets, δ-cells, like α- and β-, are innervated by parasympathetic and sympathetic axons whereas, in humans, innervation is less clear (Rodriguez-Diaz et al. 2011a).”

“By the first week of birth (P6), whereas an enrichment of TH-positive sympathetic fibers was observed at the periphery of islets in control TrkA animals (Figure 1G, arrows) (Burris and Hebrok, 2007; Rodriguez-Diaz et al., 2011), there was a complete loss of sympathetic innervation in the pancreas and several other per…”

“Innervation Only a small proportion of β cells receive an axon terminal Mouse and human Woods & Porte(63); Rodriguez-Diaz et al.(65) R E V I E W S”

“We conducted immunohistochemical studies on mouse pancreatic sections and found that tyrosine hydroxylase-positive sympathetic axons were in close contact with αSMA-positive pericytes [Figure 7A; see also (Rodriguez-Diaz et al., 2011)].”

“On the other hand, the endocrine parenchyma of the mouse islet is densely innervated by autonomic axons, whereas in the human islet autonomic axons predominantly contact vascular smooth muscle cells [10].”

“This is yet another example where observations in rodents cannot be extrapolated to humans (5, 6, 10, 15, 32, 33).”

“Both arterioles and the endocrine cells themselves receive efferent nerves, particularly sympathetic nerve fibers, but also non-adrenergic, non-cholinergic (NANC) nerves (5,6,39).”

“In light of these findings, models for islet cholinergic signaling now should feature cholinergic input primarily from endocrine a-cells in human islets and be distinguished from cholinergic input in mouse islets, which originates mainly from parasympathetic innervation (16,47,48).”

“ing that functional regulation of endocrine cells in humans may occur indirectly by changing local islet blood flow.(52,53)”

“Local islet changes may include chronic hyperfunction of the -cell, amyloid deposition (32), altered islet vascularization (56), interaction with host exocrine pancreas (8), and neuronal signals from the central nervous system and other tissues (52).”

“1C), as they are in the native pancreas (20).”

“This observation is in line with other differences that have been noted between these species with respect to islet morphology and function, most notably the recent observation that human islets contain fewer, relatively large nerve fibres, compared with the extensive network of fine nerve fibres found in rodent islet…”

“In rodent islets, there is a clear increase in islet vascular and nerve density relative to that of the exocrine pancreas (Dai et al. 2013; Rodriguez-Diaz et al. 2011).”

“than insulin-secreting beta cells (Rodriguez-Diaz et al., 2011), reflecting catabolic and anabolic functions of these hormones respectively, were also reported (Figure 1, panel B).”

“Although still in their infancy, such studies have highlighted key structure–function differences between rodents and NHP or human islets, with evidence pointing towards a high degree of similarity between NHP and human islets [8, 14, 17, 18].”

“Although it has been suggested that the neuronal connections to pancreatic islets are to endothelial cells (34), it is nonetheless clear that the CNS can have a major influence on the functional regulation on b-cells (29,32).”

“As the majority of neuronal projections in the pancreas are targeted to pancreatic islets (13,14), it has been assumed that this approach predominantly highlights efferent brain linkage to the endocrine pancreas compared with the exocrine tissue (22,23).”

“Human islets, on the other hand, are only sparsely innervated, with most neurons contacting intraislet smooth muscle cells (1).”

“Investigators have shown that not all beta cells are in close contact with neuronal axons (Rodriguez-Diaz et al., 2011), and differences exist in the proximity and access to capillaries, which provide important factors, such as oxygen and nutrients (BonnerWeir, 1988; Cabrera et al., 2006).”

“In humans however, islets appear more autonomous from central control, as islets are sparsely innervated, rather axons are associated with smooth muscle cells of blood vessels within the islets [5].”

“In contrast, rodent islet vasculature is primarily composed of endothelial tubes, with only a few arterioles containing smooth muscle cells (Bonner-Weir and Orci, 1982; Rodriguez-Diaz et al., 2011a).”

“The innervation of mouse and human islets is rather different (46).”

“Although the sympathetic nerves of the human islet do not directly contact islet endocrine cells (43,44), as they do in mice (44), activation of sympathetic nerves still influences islet hormone secretion in human subjects (45).”

“limited neural–islet associations, particularly a lack of parasympathetic nerves in the islet [35, 36], the improved imaging approach used here with tissue clearing has”

“Thus, our modified technique may be particularly useful for studying the vascular system in pancreatic function and homeostasis [4,9].”

“This observation adds to the previously reported differences between human and rodent islets (25,37,38).”

“More specifically, DIT, which depends on autonomic outflow (Ahrén, 2000; Rodriguez-Diaz et al., 2011; Taborsky, 2011), is diminished when sweetness is either too sweet or not sweet enough given the caloric load.”

“In mice, sympathetic innervation is localized largely at the islet periphery, with nerves making direct contacts with glucagon-secreting α cells (Figure 1A) [5].”

“Both sympathetic and parasympathetic nerve fibers are affected by changes in VEGF expression Mouse pancreatic islets are primarily innervated by autonomic nerves (Ahrén, 2000; Rodriguez-Diaz et al., 2011a).”

“Such relationships have been shown between sympathetic nerve varicosities and both α- and δ- cells, although less so with β-cells [451].”

“Donor pancreas islet innervation and vasculature, important for coordinated islet function in vivo (8, 14), were normal (Supplemental Figure 1I).”

“18 Thus, human islets are relatively devoid of parasympathetic nerve fibres [83], and glucose19”

“In keeping with previous studies examining TH+ fibers in human pancreatic samples (3, 11), innervation density is similar in human exocrine and endocrine pancreas.”

“regulate β-cell mass [42], while macrophages promote β-cell regeneration [43].”

“may be of relevance, although even in human islets rare connections are still seen between neurons and β-cells.(100) It must be emphasized that the studies reported up to now have used cultured islets wherein both interneurons and blood vessels have largely collapsed.”

“Indeed, the clinical and pathological features in non-human primate models of T2D impeccably reflect those of human T2D, making the translation of novel therapeutic agents from non-human primates to humans highly predictive Hansen, 2012; Harwood et al., 2012).”

“parasympathetic and sympathetic neurons [4].”

“Whether these considerations apply to human islets, in which the beta cell and alpha cell compartments are not as regionally distinct as in rodents [58, 81], andwhose innervation also appearsmuch sparser than in rodents [82, 83], remain to be shown.”

“In contrast, in humans, sympathetic fibers target the islet vasculature while parasympathetic fibers are rare: alpha cells control the supply of acetylcholine to beta and delta cells [156,157,191].”

“Notable differences have been revealed between rodent and human islets, including variations in innervation (5), vascularization (5–7), cell type composition (8), hormone secretion (8), islet-enriched transcription factor distribution (9), mitogenic stimuli (10), and stress response signaling (11).”

“Innervation was not observed to be widespread in the islet [54] Vascular perfusion was observed to follow a core to mantle direction [55] Blood vessels were reported to penetrate the b-cell core of the islet [11] Islet Composition The human pancreas can be partitioned in PP-rich and PP-poor lobes [13] PP-cells are enr…”

“…by signals able to evoke beta cell [Ca2+]c responses that stem from local sources and conceivably stimulate some beta cells more than others, for instance ATP, acetylcholine, or glucagon released from parasympathetic nerve endings or alpha cells (Rodriguez-Diaz et al., 2011a,b; Gylfe et al., 2012).”

“We successfully used antibodies to vAChT to reveal the cholinergic phenotype of a-cells, but the immunostaining results depended on the processing and quality of the human pancreas preparation (60,64).”

“However, in the sympathetic division of the mouse islet autonomic nerves (which will be discussed in the section ‘Sympathetic Innervation’), because the islet β-cells do not receive a direct sympathetic input [19,41], similar loss of the islet sympathetic innervation was not seen in moderate insulitis in NOD mice [19].”

“[41, 42].”

“Consistent with a previous report 27 , YFP-positive nerve fibres made contact with both β and α cells, which are positive for insulin and glucagon, respectively (Fig.”