Histopathology of the dermo-epidermal junction in the lamellar region of front claws was examined in 6 dairy heifers given an alimentary oligofructose overload and compared with sections from a control group of 6 heifers. Four of the 6 heifers administered oligofructose developed clinical signs of acute laminitis before they were euthanized. Postmortem samples from front claws were processed for histology. Eleven histopathologic characteristics were selected from the existing literature and used in a blinded evaluation of sections. In total, 104 front claw samples, including 8 samples from 2 cows having spontaneously occurring acute laminitis, were evaluated histologically using hematoxylin and eosin as well as periodic acid-Schiff staining. The major morphological features associated with oligofructose-induced acute clinical laminitis were stretching of lamellae, dermal edema, hemorrhage, changes in basal cell morphology, presence of white blood cells in dermis, and signs of basement membrane detachment. Changes at the lamellar junction of claw tissue affected by oligofructose-induced clinical laminitis resembled tissue from the 2 cows suffering from spontaneous acute clinical laminitis, and generally were consistent with existing descriptions of laminitis histopathology. Important exceptions to existing descriptions in the literature were stretching of lamellae and basement membrane changes. Not previously described, we considered these early signs of acute laminitis. In conclusion, this study documents that oligofructose-induced clinical laminitis is associated with histopathological changes at the lamellar interface. A weakened dermo-epidermal junction is a possible intermediate stage in the pathophysiology of bovine sole ulceration at the typical site.

Like obesity, prolonged food deprivation induces severe hepatic steatosis; however, the functional significance of this phenomenon is not well understood. In this study, we show that the fall in plasma leptin concentration during fasting is required for the development of hepatic steatosis in mice. Removal of leptin receptors from AGRP neurons diminishes fasting-induced hepatic steatosis. Furthermore, the suppressive effects of leptin on fasting-induced hepatic steatosis are absent in mice lacking the gene encoding agouti-related protein (Agrp), suggesting that this function of leptin is mediated by AGRP. Prolonged fasting leads to suppression of hepatic sympathetic activity, increased expression of acyl CoA:diacylglycerol acyltransferase-2 in the liver, and elevation of hepatic triglyceride content and all of these effects are blunted in the absence of AGRP. AGRP deficiency, despite having no effects on feeding or body adiposity in the free-fed state, impairs triglyceride and ketone body release from the liver during prolonged fasting. Furthermore, reducing CNS Agrp expression in wild-type mice by RNAi protected against the development of hepatic steatosis not only during starvation, but also in response to consumption of a high-fat diet. These findings identify the leptin-AGRP circuit as a critical modulator of hepatic triglyceride stores in starvation and suggest a vital role for this circuit in sustaining the supply of energy from the liver to extrahepatic tissues during periods of prolonged food deprivation.

Increased expression of bone morphogenetic proteins (BMPs) in several tissues is associated with inflammation and type 2 diabetes mellitus. BMP2 and BMP4 mRNA expression is increased in pancreatic islets from db/db mice and β-cell proliferation and function are inhibited by BMP4. The effect of BMPs on α-cells is currently unknown. Here, we investigate the effects of BMP4 on mouse and human α-cells in vitro. The effects of BMP4 on α-cell proliferation and function were investigated in islets isolated from male mice and from human donors, and in α-TC1-6 cells. The effects of BMP4 on α-cell function were assessed by determination of glucagon secretion and gene expression. Treatment with BMP4 for 24-96 hours inhibited glucagon secretion in a time-dependent manner in mouse and human islets. Glucagon content, preproglucagon and aristaless related homeobox mRNA expression were reduced after incubation with BMP4 in mouse islets, but not in human islets. The percentage of proliferating α-cells was reduced from 7.3 % to 0.2 % in mouse islets incubated with BMP4. α-cell proliferation in human islets ranged from 0 to 11.8 %, and BMP4 was found to inhibit proliferation of α-cells from all donors when proliferation was present. In agreement with the observations in primary islets, BMP4 decreased glucagon content, preproglucagon, and aristaless related homeobox mRNA expression in α-TC1-6 cells. Our findings suggest that BMP4 has an inhibitory role on glucagon secretion, α-cell growth, and expression of genes maintaining α-cell identity.